feat: add daemon RPC endpoints for config and mol stale (bd-ag35)

Add two new RPC endpoints to allow CLI commands to work in daemon mode:

1. GetConfig (OpGetConfig) - Retrieves config values from the daemon database.
   Used by bd create to validate issue prefix in daemon mode.

2. MolStale (OpMolStale) - Finds stale molecules (complete-but-unclosed
   epics). Used by bd mol stale command in daemon mode.

Changes:
- internal/rpc/protocol.go: Add operation constants and request/response types
- internal/rpc/client.go: Add client methods GetConfig() and MolStale()
- internal/rpc/server_issues_epics.go: Add handler implementations
- internal/rpc/server_routing_validation_diagnostics.go: Register handlers
- cmd/bd/create.go: Use GetConfig RPC instead of skipping validation
- cmd/bd/mol_stale.go: Use MolStale RPC instead of requiring --no-daemon
- internal/rpc/coverage_test.go: Add tests for new endpoints

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

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

cmd/bd/create.go

@@ -222,8 +222,12 @@ var createCmd = &cobra.Command{
 			// Get database prefix from config
 			var dbPrefix string
 			if daemonClient != nil {
-				// TODO(bd-ag35): Add RPC method to get config in daemon mode
-				// For now, skip validation in daemon mode (needs RPC enhancement)
+				// Daemon mode - use RPC to get config
+				configResp, err := daemonClient.GetConfig(&rpc.GetConfigArgs{Key: "issue_prefix"})
+				if err == nil {
+					dbPrefix = configResp.Value
+				}
+				// If error, continue without validation (non-fatal)
 			} else {
 				// Direct mode - check config
 				dbPrefix, _ = store.GetConfig(ctx, "issue_prefix")