fix: Make Mayor/Deacon session names include town name

Session names `gt-mayor` and `gt-deacon` were hardcoded, causing tmux
session name collisions when running multiple towns simultaneously.

Changed to `gt-{town}-mayor` and `gt-{town}-deacon` format (e.g.,
`gt-ai-mayor`) to allow concurrent multi-town operation.

Key changes:
- session.MayorSessionName() and DeaconSessionName() now take townName param
- Added workspace.GetTownName() helper to load town name from config
- Updated all callers in cmd/, daemon/, doctor/, mail/, rig/, templates/
- Updated tests with new session name format
- Bead IDs remain unchanged (already scoped by .beads/ directory)

Fixes #60

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

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

internal/templates/roles/boot.md.tmpl

@@ -57,7 +57,7 @@ Check the current system state:
 
 ```bash
 # Is Deacon session alive?
-tmux has-session -t gt-deacon 2>/dev/null && echo "alive" || echo "dead"
+tmux has-session -t {{ .DeaconSession }} 2>/dev/null && echo "alive" || echo "dead"
 
 # If alive, what's the pane showing?
 gt peek deacon --lines 20

internal/templates/roles/deacon.md.tmpl

@@ -244,8 +244,8 @@ This is the opposite of polecat work, which is persistent and auditable.
 
 | Role | Session Name |
 |------|-------------|
-| Deacon | `gt-deacon` (you) |
-| Mayor | `gt-mayor` |
+| Deacon | `{{ .DeaconSession }}` (you) |
+| Mayor | `{{ .MayorSession }}` |
 | Witness | `gt-<rig>-witness` |
 | Crew | `gt-<rig>-<name>` |
 
@@ -376,5 +376,5 @@ But typically just exit and let the daemon respawn you with fresh context.
 
 State directory: {{ .TownRoot }}/deacon/
 Mail identity: deacon/
-Session: gt-deacon
+Session: {{ .DeaconSession }}
 Patrol molecule: mol-deacon-patrol (created as wisp)

internal/templates/templates.go

@@ -24,14 +24,17 @@ type Templates struct {
 
 // RoleData contains information for rendering role contexts.
 type RoleData struct {
-	Role        string   // mayor, witness, refinery, polecat, crew, deacon
-	RigName     string   // e.g., "greenplace"
-	TownRoot    string   // e.g., "/Users/steve/ai"
-	WorkDir     string   // current working directory
-	Polecat     string   // polecat name (for polecat role)
-	Polecats    []string // list of polecats (for witness role)
-	BeadsDir    string   // BEADS_DIR path
-	IssuePrefix string   // beads issue prefix
+	Role           string   // mayor, witness, refinery, polecat, crew, deacon
+	RigName        string   // e.g., "greenplace"
+	TownRoot       string   // e.g., "/Users/steve/ai"
+	TownName       string   // e.g., "ai" - the town identifier for session names
+	WorkDir        string   // current working directory
+	Polecat        string   // polecat name (for polecat role)
+	Polecats       []string // list of polecats (for witness role)
+	BeadsDir       string   // BEADS_DIR path
+	IssuePrefix    string   // beads issue prefix
+	MayorSession   string   // e.g., "gt-ai-mayor" - dynamic mayor session name
+	DeaconSession  string   // e.g., "gt-ai-deacon" - dynamic deacon session name
 }
 
 // SpawnData contains information for spawn assignment messages.

internal/templates/templates_test.go

@@ -22,9 +22,12 @@ func TestRenderRole_Mayor(t *testing.T) {
 	}
 
 	data := RoleData{
-		Role:     "mayor",
-		TownRoot: "/test/town",
-		WorkDir:  "/test/town",
+		Role:          "mayor",
+		TownRoot:      "/test/town",
+		TownName:      "town",
+		WorkDir:       "/test/town",
+		MayorSession:  "gt-town-mayor",
+		DeaconSession: "gt-town-deacon",
 	}
 
 	output, err := tmpl.RenderRole("mayor", data)
@@ -51,11 +54,14 @@ func TestRenderRole_Polecat(t *testing.T) {
 	}
 
 	data := RoleData{
-		Role:     "polecat",
-		RigName:  "myrig",
-		TownRoot: "/test/town",
-		WorkDir:  "/test/town/myrig/polecats/TestCat",
-		Polecat:  "TestCat",
+		Role:          "polecat",
+		RigName:       "myrig",
+		TownRoot:      "/test/town",
+		TownName:      "town",
+		WorkDir:       "/test/town/myrig/polecats/TestCat",
+		Polecat:       "TestCat",
+		MayorSession:  "gt-town-mayor",
+		DeaconSession: "gt-town-deacon",
 	}
 
 	output, err := tmpl.RenderRole("polecat", data)
@@ -82,9 +88,12 @@ func TestRenderRole_Deacon(t *testing.T) {
 	}
 
 	data := RoleData{
-		Role:     "deacon",
-		TownRoot: "/test/town",
-		WorkDir:  "/test/town",
+		Role:          "deacon",
+		TownRoot:      "/test/town",
+		TownName:      "town",
+		WorkDir:       "/test/town",
+		MayorSession:  "gt-town-mayor",
+		DeaconSession: "gt-town-deacon",
 	}
 
 	output, err := tmpl.RenderRole("deacon", data)