feat(mnote-web): add local file read support to mnote.doc.fetch + WS push design doc

## mnote.doc.fetch: local file path support
- Detect local file paths (starting with `/` or `./`) and bypass Convex aggregate
- Read .md file directly via fs::read_to_string
- Return source: "local_fs" in response
- Support maxChars truncation for local files
- Online Convex path unchanged

## Design: WS push migration (3-14)
- New: design/03-rust-web/process/3-14-rust-web-tree-realtime-ws-push-v1.md
- Documents commit 9d8e361e WebSocket push migration rationale,
  architecture, and verification

## Updated design doc references
- 3-3: Mark SSE as fallback transport (WS push is primary)
- 08 checklist: Note WS push in Tree Realtime section
- AGENTS.md: Update tree/realtime references to reflect WS push

## Housekeeping
- desktop-hot.js: remove 3 stale log messages about disabled services
- page_ai_workflow.rs: fix 5 warnings (unused import, dead_code)

scripts/desktop-hot.js

@@ -554,7 +554,7 @@ async function main() {
     if (runtimePlan.frontendTaskName === "next-legacy") {
       logPrefix("next-legacy", `Next legacy upstream：${runtimePlan.legacyUrl}`);
     } else {
-      logPrefix("next-legacy", "desktop:hot 默认不启动历史 Next upstream，3000 由 Rust mnote-web 独占。");
+
     }
     const gatewayTask = tasks.find((task) => task.name === "mnote-web");
     if (gatewayTask) {
@@ -578,7 +578,7 @@ async function main() {
   } else if (isEnabledEnv(process.env.SKIP_BACKEND)) {
     logPrefix("backend", "已跳过 FastAPI 后端（SKIP_BACKEND=1）。");
   } else if (!shouldStartBackend(process.env)) {
-    logPrefix("backend", "默认不启动 FastAPI 后端；desktop:hot 保持 3000 单入口。如需启用请设置 ENABLE_BACKEND=1 或 BACKEND_CMD。");
+
   }
 
   if (shouldStartCelery(process.env)) {
@@ -607,7 +607,7 @@ async function main() {
   } else if (isEnabledEnv(process.env.SKIP_CELERY)) {
     logPrefix("celery", "已跳过 Celery（SKIP_CELERY=1）。");
   } else {
-    logPrefix("celery", "默认不启动 Celery；当前主线页面不依赖 Redis/Celery。如需启用请设置 ENABLE_CELERY=1 或 CELERY_CMD。");
+
   }
 
   if (tasks.length === 0) {