fix: eagerly warm extension host stores from engine TaskStores (#3340)

## Summary

Warm the extension-host task stores **up front** at dashboard startup
instead of letting the first `fn_task_*` call lazily boot a second
PostgreSQL pool per project.

## What changed

`packages/cli/src/commands/dashboard.ts`:

- After the dashboard boots, iterate every registered project (from
`centralCoreForEngine.listProjects()`) and call
`setHostTaskStore(p.path, engine.getTaskStore())` for each non-cwd
project that already has a running `ProjectEngine`.
- Reuses each engine's **existing** `TaskStore` directly — no new
backend connection, no schema advisory-lock contention, no extra
connection-pool exhaustion.
- `cwd` is skipped because its store is already injected at startup.
- Per-project failures are non-fatal (warn) and a failed project listing
logs a single warn — dashboard startup never blocks on this.
- `.changeset/extension-host-store-warmup.md` (patch, fix).

## Why

Left on its own, the first extension tool call (`fn_task_update`,
`fn_task_archive`, `fn_agent_show`, …) for a non-cwd project falls
through to `createTaskStoreForBackend`, which boots a **second**
PostgreSQL connection pool on demand. On busy hosts that lazy boot can
time out, or the call stalls behind pool/startup contention — the
classic "first `fn_task_*` call is slow or errors" experience.
Pre-populating from the already-running engines removes that lazy
worst-case path entirely.

## Verification

- `pnpm verify:fast` — PASS (13 steps, 115s): CLI `tsup` build green,
scoped typecheck/build green, boot smoke green (`fn --help` + real
`serve` with `GET /api/health` 200).
- Cherry-picked cleanly onto current `origin/main` (`5532019fd`); branch
is up-to-date with `origin/main` at PR time.

## Files

- `packages/cli/src/commands/dashboard.ts` (+30)
- `.changeset/extension-host-store-warmup.md` (new)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Bug Fixes**
* Improved dashboard startup reliability by reusing existing project
task connections.
* Prevented extension task tools from creating duplicate connection
pools.
* Added non-blocking warnings when individual project initialization or
discovery fails.
* Dashboard startup now reports how many project task stores were
successfully prepared.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: gsxdsm <gsxdsm@users.noreply.github.com>

.changeset/extension-host-store-warmup.md

@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Warm extension-host task stores up front so fn_task_* tools never hit a lazy second-pool boot.
+category: fix
+dev: Populates setHostTaskStore for every registered project from the already-running ProjectEngine TaskStores at dashboard startup, so extension API tools (fn_task_update, fn_task_archive, fn_agent_show) find a cached store and never fall through to createTaskStoreForBackend, which could time out creating a second connection pool. cwd is skipped because its store is already injected. Non-fatal warnings on any per-project failure.

packages/cli/src/commands/dashboard.ts

@@ -2272,6 +2272,36 @@ export async function runDashboard(port: number, opts: { paused?: boolean; dev?:
       }
     }
 
+    // FNXC:ExtensionHostStoreWarmup 2026-07-18-19:20:
+    // Pre-populate setHostTaskStore for all registered projects from already-
+    // running ProjectEngine TaskStores, so extension API tools (fn_task_archive,
+    // fn_task_update, etc.) find a cached store and never fall through to
+    // createTaskStoreForBackend (which times out creating a second pool).
+    // Reuses each engine's existing TaskStore directly — no new PG boot needed.
+    void (async () => {
+      try {
+        const projects = await centralCoreForEngine.listProjects();
+        // Skip cwd — its store is already injected at line 928.
+        const nonCwd = projects.filter((p) => p.path !== cwd);
+        for (const p of nonCwd) {
+          try {
+            const engine = engineManager.getEngine(p.id);
+            if (!engine) continue;
+            setHostTaskStore(p.path, engine.getTaskStore());
+          } catch (err) {
+            const msg = err instanceof Error ? err.message : String(err);
+            logSink.warn(`Failed to warm extension store for ${p.name} (${p.path}): ${msg}`, "extension");
+          }
+        }
+        if (nonCwd.length > 0) {
+          logSink.log(`Warmed extension host stores for ${nonCwd.length} project(s)`, "extension");
+        }
+      } catch (err) {
+        const msg = err instanceof Error ? err.message : String(err);
+        logSink.warn(`Failed to list projects for store warmup: ${msg}`, "extension");
+      }
+    })();
+
     disposeCallbacks.push(async () => {
       if (hybridExecutor) {
         await hybridExecutor.shutdown();