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/hooks/atlas/index.ts

@@ -44,7 +44,7 @@ You just performed direct file modifications outside \`.sisyphus/\`.
 **You are an ORCHESTRATOR, not an IMPLEMENTER.**
 
 As an orchestrator, you should:
-- **DELEGATE** implementation work to subagents via \`delegate_task\`
+- **DELEGATE** implementation work to subagents via \`task\`
 - **VERIFY** the work done by subagents
 - **COORDINATE** multiple tasks and ensure completion
 
@@ -54,7 +54,7 @@ You should NOT:
 - Implement features yourself
 
 **If you need to make changes:**
-1. Use \`delegate_task\` to delegate to an appropriate subagent
+1. Use \`task\` to delegate to an appropriate subagent
 2. Provide clear instructions in the prompt
 3. Verify the subagent's work after completion
 
@@ -128,7 +128,7 @@ You (Atlas) are attempting to directly modify a file outside \`.sisyphus/\`.
 **THIS IS FORBIDDEN** (except for VERIFICATION purposes)
 
 As an ORCHESTRATOR, you MUST:
-1. **DELEGATE** all implementation work via \`delegate_task\`
+1. **DELEGATE** all implementation work via \`task\`
 2. **VERIFY** the work done by subagents (reading files is OK)
 3. **COORDINATE** - you orchestrate, you don't implement
 
@@ -146,11 +146,11 @@ As an ORCHESTRATOR, you MUST:
 
 **IF THIS IS FOR VERIFICATION:**
 Proceed if you are verifying subagent work by making a small fix.
-But for any substantial changes, USE \`delegate_task\`.
+But for any substantial changes, USE \`task\`.
 
 **CORRECT APPROACH:**
 \`\`\`
-delegate_task(
+task(
   category="...",
   prompt="[specific single task with clear acceptance criteria]"
 )
@@ -193,7 +193,7 @@ function buildVerificationReminder(sessionId: string): string {
 
 **If ANY verification fails, use this immediately:**
 \`\`\`
-delegate_task(session_id="${sessionId}", prompt="fix: [describe the specific failure]")
+task(session_id="${sessionId}", prompt="fix: [describe the specific failure]")
 \`\`\``
 }
 
@@ -688,12 +688,12 @@ export function createAtlasHook(
         return
       }
 
-      // Check delegate_task - inject single-task directive
-      if (input.tool === "delegate_task") {
+      // Check task - inject single-task directive
+      if (input.tool === "task") {
         const prompt = output.args.prompt as string | undefined
         if (prompt && !prompt.includes(SYSTEM_DIRECTIVE_PREFIX)) {
           output.args.prompt = `<system-reminder>${SINGLE_TASK_DIRECTIVE}</system-reminder>\n` + prompt
-          log(`[${HOOK_NAME}] Injected single-task directive to delegate_task`, {
+          log(`[${HOOK_NAME}] Injected single-task directive to task`, {
             sessionID: input.sessionID,
           })
         }
@@ -732,7 +732,7 @@ export function createAtlasHook(
         return
       }
 
-      if (input.tool !== "delegate_task") {
+      if (input.tool !== "task") {
         return
       }