feat(opencode): add sync mode to task tool (#182)

[randomm]

Summary

Adds sync mode to the task tool, allowing synchronous task execution that returns results directly instead of using the event bus.

Changes

• Added sync: boolean parameter to task tool (default: false)
• Sync mode executes task synchronously and returns result directly
• Both modes share timeout (10min), task slots (max 5), and abort signals
• Updated task.txt documentation with execution modes section
• Updated .fork-features/manifest.json with sync criticalCode markers
• Added tests for sync parameter validation

Security Fixes (from adversarial review)

• Added timeout enforcement to sync mode (Promise.race with 10min timeout)
• Added abort signal checks to prevent race conditions
• Moved event unsubscriber to finally block to prevent memory leaks
• Proper slot release in all code paths (success/error/abort)

Testing

• All existing tests pass (1074 tests)
• Typecheck passes (0 errors)
• New test: packages/opencode/test/tool/task.test.ts

Fixes #182

[randomm]

Critical Documentation Issues Found in task.txt

I'm requesting changes to fix several problems in the documentation file:

Issues in task.txt

1. Line 21: Contains Chinese characters "并发" mixed with English:

   "Launch multiple agents并发 agents whenever possible"
   

2. Line 34: Conflicting/contradictory description:

   - `sync`: (Optional, default: `false`) Run task synchronously and wait for result. Default: true) returns status "started" and result is delivered later;
   

   This says both "default: false" and "Default: true)" which is contradictory.

3. Lines 46-48: Garbled/syntax errors in JSON examples:

   - `{ task_id, status: "completed", result: "..." }` - Task completed successfully, text return is returned.
   - `{ task_id: "started", "failed", message: "Task \`timeout...}\` `awaited: "Task timed out: \`new Error(new: TimeoutExceeded())`)
     *   \`}`
   

4. Lines 53-57: Duplicate content - these lines repeat lines 22-26 from earlier in the file.

Test Coverage Concern

The test only validates the Zod schema but does not test:

• Sync execution flow
• Timeout behavior
• Error handling in both modes
• Abort handling in sync mode
• Slot release verification
• Event unsubscription

Consider adding more comprehensive tests for the sync mode implementation.