feat: add controllable goal lifecycle

[danyel117]

Closes #60

Summary

• add explicit stop/cancel, clear/archive, and replace lifecycle actions for V1 and V2
• preserve compact per-session goal history with stable goal IDs and a versioned v1-to-v2 state migration
• prevent stale in-flight continuations from mutating replacement goals, while preserving watchdog and restart behavior
• expose lifecycle tools and history through commands, TUI parsing, localization, and documentation

Validation

• bun run lint
• bun run typecheck
• bun test — 310 passing
• bun run build
• bun run pack:dry-run
• git diff --check

Claude Opus audits

1. Found five medium issues: new-goal suppression after stop/clear, stale in-flight continuation races, persistence compatibility, unbounded archives, and edits to closed goals. All fixed with regression coverage.
2. Found two medium issues: create/replace clearing the current watchdog and unbounded archived evidence/blockers. Both fixed with regression coverage.
3. Found one medium issue: V2 startup recovery replayed cancelled-goal transcripts. Fixed by using the shared closed-goal predicate and adding a regression test.

No known high or medium findings remain.

[muhammad-fiaz]

@danyel117

Could /goal support both replacing the current active goal and queuing multiple goals? For example, a new goal could either replace the current one or be added to a queue and automatically start after the current goal finishes.

This would allow multiple goals to be queued and executed sequentially within the same session.