fix: relocate daemon socket for deep paths (GH#1001)

On Unix systems, socket paths are limited to 104 chars (macOS) or 108 chars
(Linux). Deep workspace paths like /Volumes/External Drive/Dropbox/...
would exceed this limit and cause daemon startup failures.

This fix:
- Adds ShortSocketPath() which computes /tmp/beads-{hash}/bd.sock for
  paths that would exceed the limit
- Keeps backward compatibility: short paths still use .beads/bd.sock
- Updates daemon discovery to check both locations
- Uses SHA256 hash of canonical workspace path for unique directories

Closes GH#1001

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

cmd/bd/daemon_autostart.go

@@ -457,13 +457,17 @@ func recordDaemonStartFailure() {
 
 // getSocketPath returns the daemon socket path based on the database location.
 // If BD_SOCKET env var is set, uses that value instead (enables test isolation).
-// Returns local socket path (.beads/bd.sock relative to database)
+// On Unix systems, uses rpc.ShortSocketPath to avoid exceeding socket path limits
+// (macOS: 104 chars) by relocating long paths to /tmp/beads-{hash}/ (GH#1001).
 func getSocketPath() string {
 	// Check environment variable first (enables test isolation)
 	if socketPath := os.Getenv("BD_SOCKET"); socketPath != "" {
 		return socketPath
 	}
-	return filepath.Join(filepath.Dir(dbPath), "bd.sock")
+	// Get workspace path (parent of .beads directory)
+	beadsDir := filepath.Dir(dbPath)
+	workspacePath := filepath.Dir(beadsDir)
+	return rpc.ShortSocketPath(workspacePath)
 }
 
 // emitVerboseWarning prints a one-line warning when falling back to direct mode