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>

cmd/bd/doctor/integrity.go

@@ -51,7 +51,7 @@ func CheckIDFormat(path string) DoctorCheck {
 	}
 
 	// Open database
-	db, err := sql.Open("sqlite3", "file:"+dbPath+"?mode=ro")
+	db, err := sql.Open("sqlite3", sqliteConnString(dbPath, true))
 	if err != nil {
 		return DoctorCheck{
 			Name:    "Issue IDs",
@@ -121,7 +121,7 @@ func CheckDependencyCycles(path string) DoctorCheck {
 	}
 
 	// Open database to check for cycles
-	db, err := sql.Open("sqlite3", dbPath)
+	db, err := sql.Open("sqlite3", sqliteConnString(dbPath, true))
 	if err != nil {
 		return DoctorCheck{
 			Name:    "Dependency Cycles",
@@ -216,7 +216,7 @@ func CheckTombstones(path string) DoctorCheck {
 		}
 	}
 
-	db, err := sql.Open("sqlite3", dbPath)
+	db, err := sql.Open("sqlite3", sqliteConnString(dbPath, true))
 	if err != nil {
 		return DoctorCheck{
 			Name:    "Tombstones",
@@ -420,7 +420,7 @@ func CheckRepoFingerprint(path string) DoctorCheck {
 	}
 
 	// Open database
-	db, err := sql.Open("sqlite3", "file:"+dbPath+"?mode=ro")
+	db, err := sql.Open("sqlite3", sqliteConnString(dbPath, true))
 	if err != nil {
 		return DoctorCheck{
 			Name:    "Repo Fingerprint",