fix(dolt): server mode should support multi-process access

Code review fix: In server mode, Dolt connects to an external sql-server
and should NOT be single-process-only. The whole point of server mode is
to enable multi-writer access.

Changes:
- Add Config.GetCapabilities() method that considers server mode
- Update daemon_guard, daemon_autostart, daemons, main to use GetCapabilities()
- Add TestGetCapabilities test
- Update init command help text to document server mode flags

The existing CapabilitiesForBackend(string) is kept for backward compatibility
but now includes a note to use Config.GetCapabilities() when the full config
is available.

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

cmd/bd/daemons.go

@@ -255,11 +255,12 @@ Stops the daemon gracefully, then starts a new one.`,
 		}
 		workspace := targetDaemon.WorkspacePath
 
-		// Guardrail: don't (re)start daemons for single-process backends (e.g., Dolt).
+		// Guardrail: don't (re)start daemons for single-process backends (e.g., embedded Dolt).
 		// This command may be run from a different workspace, so check the target workspace.
+		// Note: Dolt server mode supports multi-process, so GetCapabilities() is used.
 		targetBeadsDir := beads.FollowRedirect(filepath.Join(workspace, ".beads"))
 		if cfg, err := configfile.Load(targetBeadsDir); err == nil && cfg != nil {
-			if configfile.CapabilitiesForBackend(cfg.GetBackend()).SingleProcessOnly {
+			if cfg.GetCapabilities().SingleProcessOnly {
 				if jsonOutput {
 					outputJSON(map[string]string{"error": fmt.Sprintf("daemon mode is not supported for backend %q (single-process only)", cfg.GetBackend())})
 				} else {