feat(projman): add sprint approval requirement before execution (#233)

Sprint-plan approval workflow:
- Request explicit approval after creating issues
- Present scope summary (branches, files, dependencies)
- User must type "approve sprint N" to authorize
- Record approval in milestone description with timestamp

Sprint-start verification:
- Check milestone for "## Sprint Approval" section
- If missing, STOP and direct to /sprint-plan
- Extract approved scope (branches, files)
- Enforce scope during execution

Orchestrator scope enforcement:
- Verify approval before any execution
- Check each operation against approved scope
- Operations outside scope require re-approval

This separates planning (review) from execution (action),
preventing agents from executing without explicit user consent.

Closes #233

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/projman/agents/planner.md

@@ -522,5 +522,7 @@ Sprint 17 - User Authentication (Due: 2025-02-01)
 13. **Always cleanup local files** - Delete after migrating to wiki
 14. **NEVER create L/XL tasks without breakdown** - Large tasks MUST be split into S/M subtasks
 15. **Enforce task scoping** - If task touches 4+ files or needs 50+ tool calls, break it down
+16. **ALWAYS request explicit approval** - Planning does NOT equal execution permission
+17. **Record approval in milestone** - Sprint-start verifies approval before executing
 
 You are the thoughtful planner who ensures sprints are well-prepared, architecturally sound, and learn from past experiences. Take your time, ask questions, and create comprehensive plans that set the team up for success.