docs: describe transient drag scrolling and lifecycle limits

README.md

@@ -568,3 +568,6 @@ ui.spawn(owner,key,function) creates an owner-scoped cooperative Task for a zero
 Inside a function run by ui.spawn, `value = await task` waits for any timer/file/network/spawn Task and resumes at the same expression with its retained result. A source function may return a Number, String, managed Object or Unit; normal source annotations still apply. Task.result() and await share the result. `ui.sleep(owner,key,milliseconds)` creates a callback-free timer Task returning Unit. Plain calls/REPL can await an already completed Task; a pending await requires a coroutine and fails explicitly rather than blocking. There is no new async function declaration: ui.spawn explicitly schedules an ordinary Endor function. See examples/await-file.endor.
 
 A waiting coroutine retains its evaluated operand and frames as managed edges; waiting performs no VM execution or active 1ms spin. Source side effects and IO initiation before await are not replayed. When the dependency completes, the owning VM worker resumes the waiter through the existing fair quantum scheduler. Cancelling/replacing/closing the waiter releases its frames and operand; it does not automatically cancel an independently owned or shared dependency. Dependency cancellation propagates cancellation to its waiters without running the remainder. An unhandled dependency failure becomes a source await error (with the original provider message), fails the waiter and follows the existing shared-runtime fault rule; provider failure alone still only fails its own Task. Self-await and cyclic Task waits fail explicitly. Read-only layout/paint cannot await. Waiting state is reported as running, while active() remains true; result() is unavailable until completion. These APIs do not introduce try/finally or change the existing exception model.
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+While a native tab drag is held over an overflow arrow area, the strip waits 350ms then reveals one hidden tab every 120ms, including in a compatible destination window. The preview scroll does not activate Pages or change business state. Drawing, hit testing and insertion gaps share the same transient visible range; release uses its full-order insertion index. Leaving the strip stops the timer; release, Escape, a new press or runtime generation change restores the normal active-tab-centered strip. A resize or changing tab count clamps the range. Native drag/mixed-DPI behavior still requires platform validation; application-exit lifecycle notifications remain unfinished.

src/README.md

@@ -225,3 +225,6 @@ ui.spawn(owner,key,function) creates an owner-scoped cooperative Task for a zero
 Inside a function run by ui.spawn, `value = await task` waits for any timer/file/network/spawn Task and resumes at the same expression with its retained result. A source function may return a Number, String, managed Object or Unit; normal source annotations still apply. Task.result() and await share the result. `ui.sleep(owner,key,milliseconds)` creates a callback-free timer Task returning Unit. Plain calls/REPL can await an already completed Task; a pending await requires a coroutine and fails explicitly rather than blocking. There is no new async function declaration: ui.spawn explicitly schedules an ordinary Endor function. See examples/await-file.endor.
 
 A waiting coroutine retains its evaluated operand and frames as managed edges; waiting performs no VM execution or active 1ms spin. Source side effects and IO initiation before await are not replayed. When the dependency completes, the owning VM worker resumes the waiter through the existing fair quantum scheduler. Cancelling/replacing/closing the waiter releases its frames and operand; it does not automatically cancel an independently owned or shared dependency. Dependency cancellation propagates cancellation to its waiters without running the remainder. An unhandled dependency failure becomes a source await error (with the original provider message), fails the waiter and follows the existing shared-runtime fault rule; provider failure alone still only fails its own Task. Self-await and cyclic Task waits fail explicitly. Read-only layout/paint cannot await. Waiting state is reported as running, while active() remains true; result() is unavailable until completion. These APIs do not introduce try/finally or change the existing exception model.
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+While a native tab drag is held over an overflow arrow area, the strip waits 350ms then reveals one hidden tab every 120ms, including in a compatible destination window. The preview scroll does not activate Pages or change business state. Drawing, hit testing and insertion gaps share the same transient visible range; release uses its full-order insertion index. Leaving the strip stops the timer; release, Escape, a new press or runtime generation change restores the normal active-tab-centered strip. A resize or changing tab count clamps the range. Native drag/mixed-DPI behavior still requires platform validation; application-exit lifecycle notifications remain unfinished.

src/api.rs

@@ -1428,6 +1428,9 @@ are dynamically selected through self. Concrete native visual subclasses reuse r
 
 Window is a host-provided managed resource: ui.window(), page.window(), page.open(window), window.pages()/id()/viewport(), resize(width,height), moveTo(x,y), setTitle(text) and focus(). Requests project to their actual native window only after successful input/candidate completion and carry the current runtime session. Resize is asynchronous and the reported viewport is authoritative; this host accepts 1..4096 logical dimensions with a native 720x480 minimum. Failed input/candidates discard pending requests and read-only rendering rejects window effects. Open Pages appear in native tab chrome, with page.title, click activation/close, Ctrl+Tab cycling and Cmd/Ctrl+W close when page keyboard focus is active. Overflow arrows reach additional pages. These operations call actual Page methods in the same VM; tab IDs are weak runtime projections and add no GC roots. The 36-logical-pixel bar reduces Page constraint height; window/ui viewport reports the full inner size and native pointer positions are translated into content coordinates. Window() now creates additional native windows in the same VM, up to 16 open resources. Page.open(window)/moveToWindow(window) preserve Page and business identity while replacing Mounts; detachToWindow() creates and returns a new Window. Dragging a tab away from its strip invokes the same method. Window.close()/secondary OS close remove Page roots, unmount, and retire the resource context; retained Pages can reopen in another live window, and closed Window resources reject viewport/resize/title/focus operations. Closing the primary OS shell exits the application. Secondary viewport inputs and frame publication use the same worker. Secondary close after callback/rendering failure uses host-only teardown without invoking source callbacks or resuming execution. After reset/discard, closing an old picture never touches a fresh VM resource with the same number; viewport inputs are also generation-scoped. A teardown failure discards the affected VM and disables remaining pictures. Native initialization/surface errors are reported rather than panicking; failed secondary creation leaves a managed resource closable from Console. Native tab reordering, existing-window drops and release-point placement use the managed methods described below. Full application-exit notifications remain pending.
 
+While a native tab drag is held over an overflow arrow area, the strip waits 350ms then reveals one hidden tab every 120ms, including in a compatible destination window. The preview scroll does not activate Pages or change business state. Drawing, hit testing and insertion gaps share the same transient visible range; release uses its full-order insertion index. Leaving the strip stops the timer; release, Escape, a new press or runtime generation change restores the normal active-tab-centered strip. A resize or changing tab count clamps the range. Native drag/mixed-DPI behavior still requires platform validation; application-exit lifecycle notifications remain unfinished.
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 ContainerBlock.insert(position,block) accepts a zero-based position through the current count, returns a new stable slot and preserves existing slots/Mounts. Invalid indices and child cycles fail before changing the child list. Page.moveTab(position) uses a final zero-based index in its owning window. Native drops invoke the actual Page moveToWindow/moveTab/activate methods; a declined or redirected window move skips destination reordering. A drop allows 300000 instructions per method. Source overrides participate; earlier writes do not roll back after failure. Window.moveTo(x,y) queues the physical desktop outer origin, with signed integers within +/-1000000. Detached placement preserves the saved grab offset; the window manager may adjust it and unsupported global placement reports a diagnostic. Dragging uses a 12-logical-pixel threshold, visible insertion marker and Escape cancellation. Overflow auto-scroll, external-app occlusion and mixed-DPI verification remain pending. See examples/tab-placement.endor.
 
 Source measure and arrange overrides execute bottom-up and top-down in one read-only VM layout call. Structural Mount links exist before first measurement; bounds queries reject premature geometry. Native base layout uses current occurrence child measurements, and Arrangement must assign every stable child slot exactly once. Layout dependencies changed by lifecycle hooks trigger another pass before publication. Page constraints now use the current logical window viewport. Column/Button propagate cross-axis width and Row propagates cross-axis height; desired sizes are clamped. ui.viewport() provides a managed snapshot whose private input participates in rendering dependencies. Native resize updates are coalesced on the same worker without adding source inputs. Source measurement caches use Mount/method/children/constraints and actual subcall object reads, including returned-result decoding; Mount-reading methods conservatively bypass caching. ui.stats() exposes sourceMeasureHits/sourceMeasureMisses outside read-only rendering. Native TextBlock wrapping now uses the occurrence width in measurement/cache/painting; source measurement/arrangement now repeats until constraints and geometry settle; additional allocation policies remain pending; ScrollBlock scrolling is described below.