Polecats should auto-cleanup after MR submission

Currently polecats must manually run 'gt handoff --shutdown' after completing work. This is error-prone and leaves stale polecats around.

## Desired Flow

1. Polecat completes work
2. Polecat runs 'gt mq submit' (or similar)
3. MR is added to integration queue
4. **Polecat automatically cleans up** (no manual handoff needed)

## Implementation Options

### Option A: mq submit triggers cleanup
In 'gt mq submit':
1. Submit MR to queue
2. Automatically run cleanup (same as gt handoff --shutdown)
3. Polecat session terminates

### Option B: Refinery triggers cleanup
When Refinery picks up MR:
1. Refinery processes MR
2. Sends message to Witness: 'CLEANUP: <polecat>'
3. Witness cleans up polecat

### Option C: Molecule-driven
Define cleanup as final phase of polecat-work molecule:
1. code → test → submit-mr → cleanup

## Note
This reinforces the ephemeral model: polecats exist only for the duration of a single task.


tmux notifications: display-message too subtle, use send-keys instead

## Problem

`tmux display-message` notifications are not visible enough - they appear briefly in the status bar and are easy to miss.

## Current Behavior

router.go uses:
```go
r.tmux.DisplayMessageDefault(sessionID, notification)
```

## What Works

Sending echo commands directly to the terminal:
```bash
tmux send-keys -t <session> "echo '📬 NEW MAIL from mayor'" Enter
```

## Proposed Fix

Change notification method to send visible output to the terminal, perhaps with a box/banner:
```
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
📬 NEW MAIL from mayor
Subject: <subject>
Run: bd mail inbox
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
```

## Considerations

- This interrupts the terminal output (acceptable for important mail)
- Could check if Claude is mid-response and queue notification
- Or use tmux popup if available

Additional issues:
1. Enter key not sent properly when chained with send-keys
2. Need to debounce and send Enter separately
3. Correct pattern: send text, sleep briefly, then send Enter


gt mq submit: create MR from current branch

Implement 'gt mq submit' command that creates a merge-request bead.

Auto-detection logic:
1. Branch: current git branch
2. Issue: parse from branch name (polecat/Nux/gt-xyz → gt-xyz)
3. Target: main (or integration branch if --epic specified)
4. Worker: parse from branch name
5. Rig: current rig

Options:
- --branch BRANCH: explicit source branch
- --issue ISSUE: explicit source issue
- --epic EPIC: target integration/EPIC instead of main
- --priority P: override priority (default: inherit from source issue)

Creates merge-request bead and prints MR ID.

Reference: docs/merge-queue-design.md#creating-merge-requests


Design: Plugin architecture (agents-as-plugins)

Plugin system where plugins are just additional agents with identities, mailboxes, and beads access. See docs/architecture.md Plugins section. No special framework - just directory conventions and mail-based invocation.


Doctor check: Zombie session cleanup

Detect and clean up zombie tmux sessions via gt doctor.

## Problem

Zombie sessions occur when:
- Agent crashes without cleanup
- gt kill fails mid-operation
- System restart leaves orphan sessions
- Session naming collision

## Checks

### ZombieSessionCheck
- List all tmux sessions matching gt-* pattern
- Cross-reference with known polecats
- Flag sessions with no corresponding polecat state
- Flag sessions for removed polecats
- Check session age vs polecat creation time

### Detection Criteria
- Session exists but polecat directory doesn't
- Session name doesn't match any registered polecat
- Polecat state=idle but session running
- Multiple sessions for same polecat

## Output

```
[WARN] Zombie tmux sessions detected:
  - gt-wyvern-OldPolecat (polecat removed)
  - gt-beads-Unknown (no matching polecat)
  - gt-wyvern-Toast (duplicate session)

  Run 'gt doctor --fix' to clean up
```

## Auto-Fix (--fix flag)

- Kill orphan tmux sessions
- Update polecat state to match reality
- Log all cleanup actions

## Safety

- Never kill sessions where polecat state=working
- Prompt before killing if --fix used without --force
- Create audit log of killed sessions


Workspace doctor checks: Config, state, mail, Mayor, rigs

Workspace-level doctor checks.

## Checks

### ConfigExists
- Verify config/ directory exists
- Verify config/town.json exists
- Fix: Cannot auto-fix (need gt install)

### ConfigValid
- Parse town.json
- Verify required fields (type, version, name)
- Verify type == "town"
- Fix: Cannot auto-fix

### RigsRegistryValid
- Parse config/rigs.json
- Verify each registered rig directory exists
- Warn on missing rigs
- Fix: Remove missing rigs from registry

### MayorExists
- Verify mayor/ directory exists
- Verify mayor/CLAUDE.md exists
- Fix: Create from template

### MayorMailboxExists
- Verify mayor/mail/ directory exists
- Verify mayor/mail/inbox.jsonl exists (can be empty)
- Fix: Create directory and empty file

### MayorStateValid
- Parse mayor/state.json if exists
- Verify valid JSON
- Fix: Reset to default state

## Implementation

```go
var WorkspaceChecks = []Check{
    &ConfigExistsCheck{},
    &ConfigValidCheck{},
    &RigsRegistryValidCheck{},
    &MayorExistsCheck{},
    &MayorMailboxExistsCheck{},
    &MayorStateValidCheck{},
}
```


Add human escalation configuration

Add overseer contact config to mayor/town.json. Deacon uses this for escalation when it cannot resolve issues. Support email and/or other notification methods.


Polecat health check loop

Implement the Witness health check loop:

Every 60 seconds:
1. List active polecats (gt polecats <rig>)
2. For each polecat, check:
   - Is tmux session still alive?
   - Is there a state.json with recent update?
   - Has there been git activity recently?
3. If stuck (no activity for configurable threshold):
   - First: nudge (send message asking for status)
   - Second: escalate to Mayor
   - Third: force kill after human confirmation

This is the 'health monitor' part of Witness.


bd ready --blockers: prioritize issues that block other work

bd ready should prioritize issues that are blocking other work.

**From VC**: Blocker-first prioritization in GetReadyWork(). ~100 lines.
Algorithm: baseline-failure first, then discovered:blocker, then by priority.

**Gas Town implementation**: CLI flag or default behavior:
```bash
bd ready --blockers-first  # Or make this default
```

Checks dependency graph. Issues with many dependents surface first.

**Value**: Unblocks parallelism faster. Critical path gets cleared.

**VC lesson**: Without blocker priority, work can starve on discovered issues.


Machine registry: Store and manage machine configs

Registry for managing remote machines in federation.

## Data Model

```go
type Machine struct {
    Name     string `json:"name"`
    Type     string `json:"type"`      // "local", "ssh", "gcp"
    Host     string `json:"host"`      // for ssh: user@host
    KeyPath  string `json:"key_path"`  // SSH key path
    TownPath string `json:"town_path"` // Path to town on remote
}
```

## Interface

```go
type MachineRegistry struct {
    path     string  // config/federation.json
    machines map[string]*Machine
}

func NewMachineRegistry(configPath string) *MachineRegistry
func (r *MachineRegistry) Get(name string) (*Machine, error)
func (r *MachineRegistry) Add(m *Machine) error
func (r *MachineRegistry) Remove(name string) error
func (r *MachineRegistry) List() []*Machine
func (r *MachineRegistry) Connection(name string) (Connection, error)
```

## Storage

federation.json in config/:
```json
{
  "version": 1,
  "machines": {
    "local": {"type": "local"},
    "gcp-vm-1": {
      "type": "ssh",
      "host": "user@10.0.0.1",
      "key_path": "~/.ssh/gcp_key",
      "town_path": "/home/user/ai"
    }
  }
}
```

## Connection Factory

```go
func (r *MachineRegistry) Connection(name string) (Connection, error) {
    m := r.machines[name]
    switch m.Type {
    case "local":
        return NewLocalConnection(), nil
    case "ssh":
        return NewSSHConnection(m.Host, m.KeyPath), nil
    }
}
```


Merge: gt-xw7b

branch: polecat/morsov
target: main
source_issue: gt-xw7b
rig: gastown


Add gt crew rename command


Polecat management: add, remove, list, state

Polecat lifecycle: add, remove, list, state tracking.

## Data Model

```go
type Polecat struct {
    Name      string          `json:"name"`
    Rig       string          `json:"rig"`
    State     PolecatState    `json:"state"`
    ClonePath string          `json:"clone_path"`
    Branch    string          `json:"branch"`
    Issue     string          `json:"issue,omitempty"`
    CreatedAt time.Time       `json:"created_at"`
    UpdatedAt time.Time       `json:"updated_at"`
}

type PolecatState string
const (
    StateIdle       PolecatState = "idle"
    StateActive     PolecatState = "active"
    StateWorking    PolecatState = "working"
    StateDone       PolecatState = "done"
    StateStuck      PolecatState = "stuck"
)
```

## Interface

```go
type PolecatManager struct {
    rig *Rig
    git *Git
}

func NewPolecatManager(rig *Rig, git *Git) *PolecatManager

// Lifecycle
func (pm *PolecatManager) Add(name string) (*Polecat, error)
func (pm *PolecatManager) Remove(name string) error
func (pm *PolecatManager) List() ([]*Polecat, error)
func (pm *PolecatManager) Get(name string) (*Polecat, error)

// State
func (pm *PolecatManager) SetState(name string, state PolecatState) error
func (pm *PolecatManager) AssignIssue(name, issue string) error
func (pm *PolecatManager) ClearIssue(name string) error

// Convenience
func (pm *PolecatManager) Wake(name string) error   // idle → active
func (pm *PolecatManager) Sleep(name string) error  // active → idle
```

## Add Flow

1. Create directory: `<rig>/polecats/<name>/`
2. Clone rig repo into it (or copy from rig root)
3. Create new branch: `polecat/<name>`
4. Initialize polecat state file
5. Create mail inbox

## Remove Flow

1. Verify session not running
2. Check for uncommitted changes (warn/error)
3. Remove directory
4. Clean up state

## State Persistence

Store in `<rig>/polecats/<name>/state.json`


Merge: gt-3x1

branch: polecat/Slit
target: main
source_issue: gt-3x1
rig: gastown