docs: explain Tessera modules and execution flows in Chinese

scripts/render-uml.mjs

@@ -7,6 +7,7 @@ import path from 'node:path';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 
 const tools = process.env.UML_RENDER_TOOLS;
+// 工具依赖放在独立目录，避免给应用运行依赖增加文档渲染包。
 if (!tools) throw new Error('Set UML_RENDER_TOOLS to the documentation tool directory; see docs/architecture/uml/README.md');
 const require = createRequire(path.join(path.resolve(tools), 'package.json'));
 const { createCanvas } = require('@napi-rs/canvas');
@@ -23,6 +24,7 @@ const document = new DOMImplementation().createDocument(null, 'root', null);
 const element = document.createElement.bind(document);
 const elementNS = document.createElementNS.bind(document);
 function measurementCanvas() {
+  // PlantUML 的文本布局需要真实字体宽高，统一用本机 Canvas 测量而非固定字符宽度。
   const canvas = createCanvas(1, 1);
   const context = canvas.getContext('2d');
   const measure = context.measureText.bind(context);
@@ -41,6 +43,7 @@ function measurementCanvas() {
 }
 document.createElement = tag => tag === 'canvas' ? measurementCanvas() : element(tag);
 document.createElementNS = (namespace, tag) => {
+  // 为无浏览器 DOM 补齐样式与 getBBox，满足官方渲染引擎的 SVG 文本布局需求。
   const node = elementNS(namespace, tag);
   node.style = {};
   node.getBBox = () => {
@@ -65,6 +68,7 @@ const source = path.join(root, 'docs/architecture/uml');
 const output = path.join(source, 'rendered');
 await mkdir(output, { recursive: true });
 for (const filename of (await readdir(source)).filter(name => name.endsWith('.puml')).sort()) {
+  // 每张图独立渲染并检查错误文本；错误图不能被当作正常产物覆盖已有预览。
   const text = await readFile(path.join(source, filename), 'utf8');
   const rendered = await new Promise((resolve, reject) => renderToString(text.split('\n'), resolve, reject));
   const xml = new DOMParser().parseFromString(rendered, 'image/svg+xml');
@@ -77,6 +81,7 @@ for (const filename of (await readdir(source)).filter(name => name.endsWith('.pu
   for (const [key, value] of Object.entries({ x: '0', y: '0', width: '100%', height: '100%', fill: '#FFFFFF' })) paper.setAttribute(key, value);
   xml.documentElement.insertBefore(paper, xml.documentElement.firstChild);
   const svg = new XMLSerializer().serializeToString(xml);
+  // 同时保存可缩放 SVG 和通用 PNG；写完读取 PNG 元数据确认生成尺寸。
   const stem = filename.slice(0, -5);
   await writeFile(path.join(output, `${stem}.svg`), svg);
   // High-resolution PNG is the universally visible Markdown preview; SVG keeps zoomable text.