feat(rpc): add AllowStale option to List API (bd-dpkdm)

Add AllowStale field to ListArgs struct to support resilient hook detection.
When set, callers signal they accept potentially stale data rather than
failing on staleness check errors.

This enables gastown checkSlungWork() to fall back gracefully when the
beads database is out of sync with JSONL (common after concurrent agent syncs).

- Add AllowStale bool to ListArgs in internal/rpc/protocol.go
- Pass --allow-stale flag through to RPC in cmd/bd/list.go

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

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/rpc/protocol.go

@@ -255,6 +255,9 @@ type ListArgs struct {
 	DueAfter    string `json:"due_after,omitempty"`    // ISO 8601 format
 	DueBefore   string `json:"due_before,omitempty"`   // ISO 8601 format
 	Overdue     bool   `json:"overdue,omitempty"`      // Filter issues where due_at < now
+
+	// Staleness control (bd-dpkdm)
+	AllowStale bool `json:"allow_stale,omitempty"` // Skip staleness check, return potentially stale data
 }
 
 // CountArgs represents arguments for the count operation