fix: gt commands follow .beads/redirect for shared beads (gt-ln5af)

Added ResolveBeadsDir() helper that follows .beads/redirect files,
enabling crew workers and polecats to properly access shared beads.

Updated callers:
- mailbox.go: NewMailboxFromAddress follows redirect
- catalog.go: LoadCatalog follows redirect at all levels
- doctor checks: beads_check, patrol_check, wisp_check follow redirect

Also added comprehensive tests for the redirect resolution logic.

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

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

internal/doctor/beads_check.go

@@ -76,8 +76,9 @@ func (c *BeadsDatabaseCheck) Run(ctx *CheckContext) *CheckResult {
 	}
 
 	// Also check rig-level beads if a rig is specified
+	// Follows redirect if present (rig root may redirect to mayor/rig/.beads)
 	if ctx.RigName != "" {
-		rigBeadsDir := filepath.Join(ctx.RigPath(), ".beads")
+		rigBeadsDir := beads.ResolveBeadsDir(ctx.RigPath())
 		if _, err := os.Stat(rigBeadsDir); err == nil {
 			rigDB := filepath.Join(rigBeadsDir, "issues.db")
 			rigJSONL := filepath.Join(rigBeadsDir, "issues.jsonl")
@@ -135,9 +136,9 @@ func (c *BeadsDatabaseCheck) Fix(ctx *CheckContext) error {
 		}
 	}
 
-	// Also fix rig-level if specified
+	// Also fix rig-level if specified (follows redirect if present)
 	if ctx.RigName != "" {
-		rigBeadsDir := filepath.Join(ctx.RigPath(), ".beads")
+		rigBeadsDir := beads.ResolveBeadsDir(ctx.RigPath())
 		rigDB := filepath.Join(rigBeadsDir, "issues.db")
 		rigJSONL := filepath.Join(rigBeadsDir, "issues.jsonl")