fix(refinery): use mayor/rig fallback for correct git remote

Refinery was using rig.Path which found the town's .git with rig-named
remotes (e.g., 'gastown') instead of 'origin'. This caused refinery to
miss polecat branches when fetching.

Now falls back to mayor/rig (which has 'origin' pointing to the project
repo) when refinery/rig doesn't exist.

Fixes: hq-uvrzt

internal/refinery/engineer.go

@@ -94,13 +94,21 @@ func NewEngineer(r *rig.Rig) *Engineer {
 	// Override target branch with rig's configured default branch
 	cfg.TargetBranch = r.DefaultBranch()
 
+	// Determine the git working directory for refinery operations.
+	// Prefer refinery/rig worktree, fall back to mayor/rig (legacy architecture).
+	// Using rig.Path directly would find town's .git with rig-named remotes instead of "origin".
+	gitDir := filepath.Join(r.Path, "refinery", "rig")
+	if _, err := os.Stat(gitDir); os.IsNotExist(err) {
+		gitDir = filepath.Join(r.Path, "mayor", "rig")
+	}
+
 	return &Engineer{
 		rig:         r,
 		beads:       beads.New(r.Path),
 		mrQueue:     mrqueue.New(r.Path),
-		git:         git.NewGit(r.Path),
+		git:         git.NewGit(gitDir),
 		config:      cfg,
-		workDir:     r.Path,
+		workDir:     gitDir,
 		output:      os.Stdout,
 		eventLogger: mrqueue.NewEventLoggerFromRig(r.Path),
 		router:      mail.NewRouter(r.Path),

internal/refinery/manager.go

@@ -162,8 +162,9 @@ func (m *Manager) Start(foreground bool) error {
 	// Working directory is the refinery worktree (shares .git with mayor/polecats)
 	refineryRigDir := filepath.Join(m.rig.Path, "refinery", "rig")
 	if _, err := os.Stat(refineryRigDir); os.IsNotExist(err) {
-		// Fall back to rig path if refinery/rig doesn't exist
-		refineryRigDir = m.workDir
+		// Fall back to mayor/rig (legacy architecture) - ensures we use project git, not town git.
+		// Using rig.Path directly would find town's .git with rig-named remotes instead of "origin".
+		refineryRigDir = filepath.Join(m.rig.Path, "mayor", "rig")
 	}
 
 	// Ensure runtime settings exist in refinery/ (not refinery/rig/) so we don't