refactor: remove unused bd pin/unpin/hook commands (bd-x0zl)

Analysis found these commands are dead code:
- gt never calls `bd pin` - uses `bd update --status=pinned` instead
- Beads.Pin() wrapper exists but is never called
- bd hook functionality duplicated by gt mol status
- Code comment says "pinned field is cosmetic for bd hook visibility"

Removed:
- cmd/bd/pin.go
- cmd/bd/unpin.go
- cmd/bd/hook.go

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

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

Makefile

@@ -13,7 +13,7 @@ build:
 # Run all tests (skips known broken tests listed in .test-skip)
 test:
 	@echo "Running tests..."
-	@./scripts/test.sh
+	@TEST_COVER=1 ./scripts/test.sh
 
 # Run performance benchmarks (10K and 20K issue databases with automatic CPU profiling)
 # Generates CPU profile: internal/storage/sqlite/bench-cpu-<timestamp>.prof