chore: remove .beads/issues.jsonl and gitignore it (#1577)

## Summary
- Removes `.beads/issues.jsonl` that was accidentally committed in #1574
- Adds `.beads/issues.jsonl` to `.gitignore` to prevent recurrence

The beads passive export file is a local Dolt DB artifact and should not
be tracked in git.

## Test plan
- [x] `.gitignore` blocks the file (confirmed — auto-export hook was
blocked post-commit)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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## Summary by CodeRabbit

* **Chores**
  * Cleared local issue tracker records from project files.
* Updated repository gitignore configuration to exclude local issue
tracker export files from version control.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Co-authored-by: Ambient Code Bot <bot@ambient-code.local>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people