fix(dolt): recognize shim hooks as Dolt-compatible

Shim hooks (bd-shim marker) delegate to 'bd hook' command which already
handles Dolt backend correctly. Update both doctor check and migration
warning to recognize shim hooks as OK.

Only inline hooks (older style with embedded logic) need the explicit
Dolt backend check in the shell script.

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

cmd/bd/migrate_dolt.go

@@ -172,16 +172,24 @@ func hooksNeedDoltUpdate(beadsDir string) bool {
 		return false // No hook installed
 	}
 
-	// Check if it's a bd hook and lacks the Dolt skip logic
 	contentStr := string(content)
+
+	// Shim hooks (bd-shim) delegate to 'bd hook' which handles Dolt correctly
+	if strings.Contains(contentStr, "bd-shim") {
+		return false // Shim hooks are fine
+	}
+
+	// Check if it's a bd inline hook
 	if !strings.Contains(contentStr, "bd") {
 		return false // Not a bd hook
 	}
+
+	// Check if inline hook has the Dolt skip logic
 	if strings.Contains(contentStr, `"backend"`) && strings.Contains(contentStr, `"dolt"`) {
 		return false // Already has Dolt check
 	}
 
-	return true // bd hook without Dolt check
+	return true // bd inline hook without Dolt check
 }
 
 // handleToSQLiteMigration migrates from Dolt to SQLite backend (escape hatch).