feat(async-tasks): increase default subagent timeout from 10 to 30 minutes

[randomm]

Task Description

Increase the default subagent/task execution timeout from 10 minutes to 30 minutes in both independent timeout locations.

Background

Research revealed two independent hardcoded timeout constants (not shared):

1. packages/opencode/src/session/async-tasks.ts line 52: DEFAULT_TASK_TIMEOUT = 10 * 60 * 1000 — controls background/async task execution
2. packages/opencode/src/tool/task.ts line 381: taskTimeoutMs = 10 * 60 * 1000 — controls sync task tool execution

The current 10-minute default (already increased from upstream's 5 minutes) is still too short for complex agentic tasks such as multi-file implementations, upstream syncs, and thorough research sessions.

The existing task-timeout entry in .fork-features/manifest.json also needs correcting — it only lists async-tasks.ts in modifiedFiles but is missing tool/task.ts, which is the second independent location.

Changes Required

1. packages/opencode/src/session/async-tasks.ts — change DEFAULT_TASK_TIMEOUT from 10 * 60 * 1000 to 30 * 60 * 1000
2. packages/opencode/src/tool/task.ts — change taskTimeoutMs from 10 * 60 * 1000 to 30 * 60 * 1000
3. .fork-features/manifest.json — update task-timeout entry:
   • Add tool/task.ts to modifiedFiles
   • Update description to reflect 30-minute default and correct both locations
   • Update criticalCode markers to 30 * 60 * 1000

Quality Gates (Non-Negotiable)

• Both timeout locations updated
• Manifest task-timeout entry updated with correct modifiedFiles, description, and criticalCode
• bun run typecheck passes (0 errors)
• bun test passes (0 failures)
• bun run .fork-features/verify.ts passes

Acceptance Criteria

• Both async-tasks.ts and task.ts use 30 * 60 * 1000 as timeout
• Manifest accurately reflects both modified files and new timeout value
• All local checks pass before push