refactor: remove legacy .beads-wisp infrastructure (gt-5klh)

Wisps are now just a flag on regular beads issues (Wisp=true).
No separate directory needed - hooks stored in .beads/.

Changes:
- wisp package: WispDir now points to .beads/, removed PatrolCycle
- manager.go: removed initWispBeads() - no separate dir to create
- mrqueue.go: MRs stored in .beads/mq/ instead of .beads-wisp/mq/
- doctor: removed obsolete wisp directory checks
- docs: updated wisp-architecture.md to reflect simplified model

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

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

.gitignore

@@ -29,6 +29,3 @@ gt
 # Runtime state
 state.json
 .runtime/
-
-# Ephemeral wisps (never tracked)
-.beads-wisp/