feat: worker pre-flight verification before Claude launch in taskMaestro

[JeremyDev87]

Purpose

Workers launch with stale artifacts, missing deps, or wrong state. Pre-flight check prevents wasted cycles.

Solution

Add to taskMaestro start, after worktree creation, before Claude launch:

1. Remove stale artifacts: rm -f RESULT.json TASK.md
2. Verify node_modules (symlink or install)
3. Verify git status clean
4. Copy settings.local.json for permissions

References

• Incidents: stale RESULT.json inheritance, node_modules missing, permission prompts
• Parent: Improve taskMaestro orchestration reliability (session 2 retrospective) #900

[JeremyDev87]

Implemented in PR #918 (batch update)