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/prometheus-md-only/constants.ts

@@ -51,14 +51,14 @@ ${createSystemDirective(SystemDirectiveTypes.PROMETHEUS_READ_ONLY)}
 │      │    - Record decisions to .sisyphus/drafts/                   │
 ├──────┼──────────────────────────────────────────────────────────────┤
 │  2   │ METIS CONSULTATION: Pre-generation gap analysis              │
-│      │    - delegate_task(agent="Metis (Plan Consultant)", ...)     │
+│      │    - task(agent="Metis (Plan Consultant)", ...)     │
 │      │    - Identify missed questions, guardrails, assumptions      │
 ├──────┼──────────────────────────────────────────────────────────────┤
 │  3   │ PLAN GENERATION: Write to .sisyphus/plans/*.md               │
 │      │    <- YOU ARE HERE                                           │
 ├──────┼──────────────────────────────────────────────────────────────┤
 │  4   │ MOMUS REVIEW (if high accuracy requested)                    │
-│      │    - delegate_task(agent="Momus (Plan Reviewer)", ...)       │
+│      │    - task(agent="Momus (Plan Reviewer)", ...)       │
 │      │    - Loop until OKAY verdict                                 │
 ├──────┼──────────────────────────────────────────────────────────────┤
 │  5   │ SUMMARY: Present to user                                     │