docs: record authorized runner root filesystem expansion

Reviewed-on: #7

.gitea/workflows/env-probe.yml

@@ -29,3 +29,20 @@ jobs:
           (find / -maxdepth 4 \( -name 'lake-manifest.json' -o -name '.lake' \) -not -path '/proc/*' 2>/dev/null | head -20) || true
           (docker images 2>&1 | head -20) || true
           (docker ps -a 2>&1 | head -10) || true
+      - name: Read-only storage diagnosis
+        run: |
+          set -eu
+          hostname
+          lsblk -e 7 -o NAME,PATH,SIZE,FSTYPE,MOUNTPOINTS
+          findmnt -T /var/lib/docker
+          df -hT / /var/lib/docker
+          docker info --format 'storage={{.Driver}} root={{.DockerRootDir}}'
+          docker system df
+          docker builder du 2>/dev/null || true
+          for dir in /var/lib/docker /var/lib/containerd /opt/lean-cache /var/cache /tmp /var/log; do
+            if [ -d "$dir" ]; then du -xhd1 "$dir" 2>/dev/null || true; fi
+          done
+          for tool in sfdisk growpart resize2fs xfs_growfs; do command -v "$tool" || true; done
+          if [ "$(hostname)" = "iZ6we8b3jgd6nc2qehu06lZ" ] && command -v growpart >/dev/null; then
+            growpart -N /dev/nvme0n1 3 || true
+          fi

.gitea/workflows/runner-storage-maintenance.yml

@@ -0,0 +1,49 @@
+name: runner-storage-maintenance
+
+# Manual-only. Never runs on push or pull_request.
+on:
+  workflow_dispatch:
+    inputs:
+      confirm:
+        description: Enter EXPAND_RUNNER_ROOT after owner approval
+        required: true
+        type: string
+
+jobs:
+  expand-root:
+    if: ${{ github.event_name == 'workflow_dispatch' && inputs.confirm == 'EXPAND_RUNNER_ROOT' }}
+    runs-on: ubuntu24.04-x64-lean4.35
+    timeout-minutes: 20
+    steps:
+      - name: Back up partition table and expand the authorized ext4 root
+        run: |
+          # Owner-authorized manual-only root partition/filesystem expansion.
+          set -euo pipefail
+          exec 9>/var/lock/lean-bench-root-maintenance.lock
+          flock -n 9
+          [ "$(hostname)" = "iZ6we8b3jgd6nc2qehu06lZ" ]
+          [ "$(id -u)" = 0 ]
+          [ "$(blkid -s PARTUUID -o value /dev/nvme0n1p3 | tr A-Z a-z)" = 9b694bad-5bbb-4485-860f-e5544ae47410 ]
+          [ "$(findmnt -n -o SOURCE /)" = /dev/nvme0n1p3 ]
+          [ "$(findmnt -n -o FSTYPE /)" = ext4 ]
+          [ "$(lsblk -n -o START /dev/nvme0n1p3 | tr -d ' ')" = 413696 ]
+          [ "$(blockdev --getsize64 /dev/nvme0n1)" -ge 161061273600 ]
+          backup_dir="/root/lean-bench-maintenance/$(date -u +%Y%m%dT%H%M%SZ)"
+          install -d -m 700 "$backup_dir"
+          sfdisk --dump /dev/nvme0n1 > "$backup_dir/nvme0n1.sfdisk"
+          sync
+          printf 'Partition-table backup: %s\n' "$backup_dir/nvme0n1.sfdisk"
+          set +e
+          growpart -N /dev/nvme0n1 3 > "$backup_dir/growpart-dry-run.log" 2>&1
+          probe_status=$?
+          set -e
+          if [ "$probe_status" = 0 ]; then
+            growpart /dev/nvme0n1 3
+          elif ! grep -q '^NOCHANGE:' "$backup_dir/growpart-dry-run.log"; then
+            cat "$backup_dir/growpart-dry-run.log"
+            exit "$probe_status"
+          fi
+          resize2fs /dev/nvme0n1p3
+          [ "$(lsblk -n -o START /dev/nvme0n1p3 | tr -d ' ')" = 413696 ]
+          lsblk -e 7 -o NAME,PATH,SIZE,FSTYPE,MOUNTPOINTS
+          df -hT / /var/lib/docker

docs/infrastructure/runner-lean435.md

@@ -3,7 +3,7 @@
 Gitea runner `iZ6we8b3jgd6nc2qehu06lZ` (act_runner v5.2.0, runner id 7), label `ubuntu24.04-x64-lean4.35`. Both `lean-bench` and `lean-agent` CI run here; the old `gitea-cicd-server-for-CODEX` label is no longer used.
 
 ## The host
-- Jobs run **on the host, not in a container**, as root. Ubuntu 24.04.5, kernel 6.8, 4 CPU, 15 GiB RAM, no swap, 99 GB disk (88 GB free at setup).
+- Jobs run **on the host, not in a container**, as root. Ubuntu 24.04.5, kernel 6.8, 4 CPU, 15 GiB RAM, no swap, 150 GiB system disk (expanded from 100 GiB on 2026-10-28); the ext4 root filesystem reports about 148 GiB, with 75 GiB available immediately after expansion.
 - Lean 4.35.0 via elan 4.2.4 in `/root/.elan`. Python 3.12.3, git 2.43, gcc 13.3, curl, jq.
 - **No Node**, so `actions/checkout` and other JavaScript actions cannot run. Workflows clone with `git fetch --depth 1 origin $SHA` using `${{ github.token }}`.
 - Docker was not installed; the lean-bench `image` job installs `docker.io` + `docker-buildx` (Docker 29.1.3) if missing.
@@ -20,3 +20,30 @@ Gitea runner `iZ6we8b3jgd6nc2qehu06lZ` (act_runner v5.2.0, runner id 7), label `
 - Mathlib's post-update hook runs the cache fetch **inside `lake update`**, so retries placed after it never run. Set `MATHLIB_NO_CACHE_ON_UPDATE=1` for `lake update` and fetch in a retry loop. In the image the archives live in a BuildKit cache mount (`/root/.cache/mathlib`), so a retried build resumes.
 - Cold image build about 19 min; with layers cached about 2 min.
 - Gitea 1.26.1 has no cancel-run API; a person cancels in the web UI, then the API can `DELETE` the finished run. The Actions logs endpoint needs a token; the runs/jobs status endpoints work anonymously on this public repo.
+
+## Root capacity expansion (2026-10-28)
+
+The owner expanded the cloud disk to 150 GiB, but root partition `/dev/nvme0n1p3`
+and its ext4 filesystem still occupied about 100 GiB. CI run number 43 (API run ID 438)
+therefore continued to report 28 GiB available and failed its unchanged 30 GiB preflight.
+Rerunning a failed job retains the same UI run number; its job attempt number increments.
+
+Read-only probe run number 45 (API run ID 442) confirmed the raw-disk/partition mismatch.
+Its `growpart -N` output showed that partition 3 could extend from 209301471 to
+314159071 sectors while keeping start sector 413696 and its partition UUID unchanged.
+Temporary files and logs were small; Docker/containerd storage and Mathlib were the main
+consumers. No tagged image, build cache or Mathlib cache was deleted for this repair.
+
+The owner explicitly authorized partition and filesystem expansion in the execution chat.
+Manual maintenance run number 46 (API run ID 443) then backed up the partition table to
+`/root/lean-bench-maintenance/20261028T121919Z/nvme0n1.sfdisk`, expanded partition 3,
+and grew the mounted ext4 filesystem online. The resulting partition is 149.8 GiB;
+`df` reported a 148 GiB filesystem with 75 GiB available. No reboot was required.
+
+`.gitea/workflows/env-probe.yml` now includes read-only storage and cache diagnostics.
+`.gitea/workflows/runner-storage-maintenance.yml` is manual-only and requires the literal
+confirmation `EXPAND_RUNNER_ROOT`. It validates hostname, root device, ext4 type, partition
+UUID, start sector and disk size, takes a lock, and backs up the partition table before any
+change. Future execution still requires explicit owner authorization for that maintenance.
+It never formats a device or prunes images. The failed image job was retried after expansion;
+its actual build, smoke-test and image-retention outcome is recorded in CI run number 43.