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>

internal/rpc/client.go

@@ -442,6 +442,36 @@ func (c *Client) GetWorkerStatus(args *GetWorkerStatusArgs) (*GetWorkerStatusRes
 	return &result, nil
 }
 
+// GetConfig retrieves a config value from the daemon's database
+func (c *Client) GetConfig(args *GetConfigArgs) (*GetConfigResponse, error) {
+	resp, err := c.Execute(OpGetConfig, args)
+	if err != nil {
+		return nil, err
+	}
+
+	var result GetConfigResponse
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal config response: %w", err)
+	}
+
+	return &result, nil
+}
+
+// MolStale retrieves stale molecules (complete-but-unclosed) via the daemon
+func (c *Client) MolStale(args *MolStaleArgs) (*MolStaleResponse, error) {
+	resp, err := c.Execute(OpMolStale, args)
+	if err != nil {
+		return nil, err
+	}
+
+	var result MolStaleResponse
+	if err := json.Unmarshal(resp.Data, &result); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal mol stale response: %w", err)
+	}
+
+	return &result, nil
+}
+
 // cleanupStaleDaemonArtifacts removes stale daemon.pid file when socket is missing and lock is free.
 // This prevents stale artifacts from accumulating after daemon crashes.
 // Only removes pid file - lock file is managed by OS (released on process exit).