refactor: migrate delegate_task to task tool with metadata fixes

- Rename delegate_task tool to task across codebase (100 files)
- Update model references: claude-opus-4-6 → 4-5, gpt-5.3-codex → 5.2-codex
- Add tool-metadata-store to restore metadata overwritten by fromPlugin()
- Add session ID polling for BackgroundManager task sessions
- Await async ctx.metadata() calls in tool executors
- Add ses_ prefix guard to getMessageDir for performance
- Harden BackgroundManager with idle deferral and error handling
- Fix duplicate task key in sisyphus-junior test object literals
- Fix unawaited showOutputToUser in ast_grep_replace
- Fix background=true → run_in_background=true in ultrawork prompt
- Fix duplicate task/task references in docs and comments

src/features/tool-metadata-store/index.ts

@@ -0,0 +1,84 @@
+/**
+ * Pending tool metadata store.
+ *
+ * OpenCode's `fromPlugin()` wrapper always replaces the metadata returned by
+ * plugin tools with `{ truncated, outputPath }`, discarding any sessionId,
+ * title, or custom metadata set during `execute()`.
+ *
+ * This store captures metadata written via `ctx.metadata()` inside execute(),
+ * then the `tool.execute.after` hook consumes it and merges it back into the
+ * result *before* the processor writes the final part to the session store.
+ *
+ * Flow:
+ *   execute() → storeToolMetadata(sessionID, callID, data)
+ *   fromPlugin() → overwrites metadata with { truncated }
+ *   tool.execute.after → consumeToolMetadata(sessionID, callID) → merges back
+ *   processor → Session.updatePart(status:"completed", metadata: result.metadata)
+ */
+
+export interface PendingToolMetadata {
+  title?: string
+  metadata?: Record<string, unknown>
+}
+
+const pendingStore = new Map<string, PendingToolMetadata & { storedAt: number }>()
+
+const STALE_TIMEOUT_MS = 15 * 60 * 1000
+
+function makeKey(sessionID: string, callID: string): string {
+  return `${sessionID}:${callID}`
+}
+
+function cleanupStaleEntries(): void {
+  const now = Date.now()
+  for (const [key, entry] of pendingStore) {
+    if (now - entry.storedAt > STALE_TIMEOUT_MS) {
+      pendingStore.delete(key)
+    }
+  }
+}
+
+/**
+ * Store metadata to be restored after fromPlugin() overwrites it.
+ * Called from tool execute() functions alongside ctx.metadata().
+ */
+export function storeToolMetadata(
+  sessionID: string,
+  callID: string,
+  data: PendingToolMetadata,
+): void {
+  cleanupStaleEntries()
+  pendingStore.set(makeKey(sessionID, callID), { ...data, storedAt: Date.now() })
+}
+
+/**
+ * Consume stored metadata (one-time read, removes from store).
+ * Called from tool.execute.after hook.
+ */
+export function consumeToolMetadata(
+  sessionID: string,
+  callID: string,
+): PendingToolMetadata | undefined {
+  const key = makeKey(sessionID, callID)
+  const stored = pendingStore.get(key)
+  if (stored) {
+    pendingStore.delete(key)
+    const { storedAt: _, ...data } = stored
+    return data
+  }
+  return undefined
+}
+
+/**
+ * Get current store size (for testing/debugging).
+ */
+export function getPendingStoreSize(): number {
+  return pendingStore.size
+}
+
+/**
+ * Clear all pending metadata (for testing).
+ */
+export function clearPendingStore(): void {
+  pendingStore.clear()
+}