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

.opencode/command/remove-deadcode.md

@@ -41,27 +41,27 @@ Fire ALL simultaneously:
 
 ```
 // Agent 1: Find all exported symbols
-delegate_task(subagent_type="explore", run_in_background=true,
+task(subagent_type="explore", run_in_background=true,
   prompt="Find ALL exported functions, classes, types, interfaces, and constants across src/.
   List each with: file path, line number, symbol name, export type (named/default).
   EXCLUDE: src/index.ts root exports, test files.
   Return as structured list.")
 
 // Agent 2: Find potentially unused files
-delegate_task(subagent_type="explore", run_in_background=true,
+task(subagent_type="explore", run_in_background=true,
   prompt="Find files in src/ that are NOT imported by any other file.
   Check import/require statements across the entire codebase.
   EXCLUDE: index.ts files, test files, entry points, config files, .md files.
   Return list of potentially orphaned files.")
 
 // Agent 3: Find unused imports within files
-delegate_task(subagent_type="explore", run_in_background=true,
+task(subagent_type="explore", run_in_background=true,
   prompt="Find unused imports across src/**/*.ts files.
   Look for import statements where the imported symbol is never referenced in the file body.
   Return: file path, line number, imported symbol name.")
 
 // Agent 4: Find functions/variables only used in their own declaration
-delegate_task(subagent_type="explore", run_in_background=true,
+task(subagent_type="explore", run_in_background=true,
   prompt="Find private/non-exported functions, variables, and types in src/**/*.ts that appear
   to have zero usage beyond their declaration. Return: file path, line number, symbol name.")
 ```

.opencode/skills/github-issue-triage/SKILL.md

@@ -21,7 +21,7 @@ You are a GitHub issue triage automation agent. Your job is to:
 
 | Aspect | Rule |
 |--------|------|
-| **Task Granularity** | 1 Issue = Exactly 1 `delegate_task()` call |
+| **Task Granularity** | 1 Issue = Exactly 1 `task()` call |
 | **Execution Mode** | `run_in_background=true` (Each issue runs independently) |
 | **Result Handling** | `background_output()` to collect results as they complete |
 | **Reporting** | IMMEDIATE streaming when each task finishes |
@@ -67,7 +67,7 @@ for (let i = 0; i < allIssues.length; i++) {
   const issue = allIssues[i]
   const category = getCategory(i)
   
-  const taskId = await delegate_task(
+  const taskId = await task(
     category=category,
     load_skills=[],
     run_in_background=true,  // ← CRITICAL: Each issue is independent background task
@@ -195,7 +195,7 @@ for (let i = 0; i < allIssues.length; i++) {
   
   console.log(`🚀 Launching background task for Issue #${issue.number} (${category})...`)
   
-  const taskId = await delegate_task(
+  const taskId = await task(
     category=category,
     load_skills=[],
     run_in_background=true,  // ← BACKGROUND TASK: Each issue runs independently
@@ -480,7 +480,7 @@ When invoked, immediately:
 4. Exhaustive pagination for issues
 5. Exhaustive pagination for PRs
 6. **LAUNCH**: For each issue:
-   - `delegate_task(run_in_background=true)` - 1 task per issue
+   - `task(run_in_background=true)` - 1 task per issue
    - Store taskId mapped to issue number
 7. **STREAM**: Poll `background_output()` for each task:
    - As each completes, immediately report result

.opencode/skills/github-pr-triage/SKILL.md

@@ -22,7 +22,7 @@ You are a GitHub Pull Request triage automation agent. Your job is to:
 
 | Aspect | Rule |
 |--------|------|
-| **Task Granularity** | 1 PR = Exactly 1 `delegate_task()` call |
+| **Task Granularity** | 1 PR = Exactly 1 `task()` call |
 | **Execution Mode** | `run_in_background=true` (Each PR runs independently) |
 | **Result Handling** | `background_output()` to collect results as they complete |
 | **Reporting** | IMMEDIATE streaming when each task finishes |
@@ -68,7 +68,7 @@ for (let i = 0; i < allPRs.length; i++) {
   const pr = allPRs[i]
   const category = getCategory(i)
   
-  const taskId = await delegate_task(
+  const taskId = await task(
     category=category,
     load_skills=[],
     run_in_background=true,  // ← CRITICAL: Each PR is independent background task
@@ -178,7 +178,7 @@ for (let i = 0; i < allPRs.length; i++) {
   
   console.log(`🚀 Launching background task for PR #${pr.number} (${category})...`)
   
-  const taskId = await delegate_task(
+  const taskId = await task(
     category=category,
     load_skills=[],
     run_in_background=true,  // ← BACKGROUND TASK: Each PR runs independently
@@ -474,7 +474,7 @@ When invoked, immediately:
 2. `gh repo view --json nameWithOwner -q .nameWithOwner`
 3. Exhaustive pagination for ALL open PRs
 4. **LAUNCH**: For each PR:
-   - `delegate_task(run_in_background=true)` - 1 task per PR
+   - `task(run_in_background=true)` - 1 task per PR
    - Store taskId mapped to PR number
 5. **STREAM**: Poll `background_output()` for each task:
    - As each completes, immediately report result