gt rig info: Show detailed rig information

Add 'gt rig info <rig>' command to show detailed rig status.

Should show:
- Rig path and git URL
- Active polecats with status
- Refinery status
- Witness status
- Recent activity
- Beads summary (open issues count)


Swarm learning: Beads database locality gap

## PGT Bug (GGT Design Already Correct)

Mayor created issues in `~/ai/mayor/rigs/beads/.beads/` but polecats use `~/ai/beads/.beads/`. Different databases = polecats can't see Mayor's beads.

**GGT Fix**: architecture.md already specifies:
- All agents use BEADS_DIR pointing to rig-level `.beads/`
- Lines 116-143: Beads Configuration for Multi-Agent
- Lines 573-586: Rig-Level Beads via BEADS_DIR

This is a PGT implementation gap, not a design issue. GGT spawn must set BEADS_DIR correctly.


gt park command for parking molecules on external deps

Add `gt park` command for when polecat hits external dependency:

```bash
gt park --step=gt-mol.3 --waiting="beads:mol-run-assignee"
```

This command:
1. Adds blocked_by: external:beads:mol-run-assignee to the step
2. Clears assignee on the step
3. Clears assignee on molecule root
4. Sends handoff mail to self with context
5. Shuts down polecat session

The molecule enters "parked" state (derived: in_progress + no assignee + blocked step).

Part of cross-project dependency system.
See: docs/cross-project-deps.md

Depends on Beads: bd-om4a (external: blocked_by support)


bd pin command fails: invalid field for update: pinned

In beads v0.32.0, `bd pin <id>` fails with 'invalid field for update: pinned'. The pinned field exists in the schema but update logic doesn't handle it.

Repro:
```
bd create 'test issue'
bd pin <id>
# Error: invalid field for update: pinned
```

Expected: Issue should be pinned.

This blocks gt mail send --pinned from working.

Fixed by adding pinned to allowedUpdateFields


Merge: gt-caih

branch: polecat/furiosa
target: main
source_issue: gt-caih
rig: gastown


Immediate daemon notification on lifecycle request

When gt handoff sends a lifecycle request to the daemon (via bd mail send deacon/), the daemon only discovers it on its next heartbeat poll (every 5 min). Workers wait unnecessarily for retirement.

## Current Behavior
1. Worker runs gt handoff
2. Lifecycle mail sent to deacon/ via beads
3. Worker blocks waiting for retirement
4. Daemon heartbeat runs (up to 5 min later)
5. Daemon processes lifecycle request and kills session

## Expected Behavior
Lifecycle requests should be processed immediately, not on poll interval.

## Proposed Solutions

### Option A: SIGUSR1 Signal (simplest)
1. Add SIGUSR1 handler in daemon that calls ProcessLifecycleRequests()
2. gt handoff reads daemon.pid and sends SIGUSR1 after mail send

### Option B: Unix Socket
1. Daemon listens on ~/gt/daemon/lifecycle.sock
2. gt handoff connects and sends 'process' message

### Option C: Watchfile + fsnotify
1. gt handoff touches ~/gt/daemon/lifecycle.trigger
2. Daemon uses fsnotify to detect and process

Recommend Option A for simplicity.

## Affected Files
- internal/daemon/daemon.go - add signal handler
- internal/cmd/handoff.go - send signal after mail


Per-rig beads repo configuration

Add per-rig beads configuration to rig config schema.

## Config Schema

In each rig's config.json:

```json
{
  "version": 1,
  "name": "wyvern",
  "git_url": "https://github.com/steveyegge/wyvern",
  "beads": {
    "repo": "local",    // "local" | "<path>" | "<git-url>"
    "root": null,       // Override bd --root (optional)
    "prefix": "wyv"     // Issue prefix for this rig
  }
}
```

## Repo Options

| Value | Meaning | Use Case |
|-------|---------|----------|
| `"local"` | Use project's `.beads/` | Own projects, full commit access |
| `"<path>"` | Use beads at path | OSS contributions |
| `"<git-url>"` | Clone and use repo | Team shared beads |

## Environment Injection

When spawning polecats, Gas Town sets:
```bash
export BEADS_ROOT="<resolved-path>"
```

## Resolution Logic

```go
func ResolveBeadsRoot(rigConfig *RigConfig, rigPath string) (string, error) {
    beads := rigConfig.Beads
    switch {
    case beads.Root != "":
        return beads.Root, nil
    case beads.Repo == "local" || beads.Repo == "":
        return filepath.Join(rigPath, ".beads"), nil
    case strings.HasPrefix(beads.Repo, "/"):
        return beads.Repo, nil
    case strings.Contains(beads.Repo, "://"):
        return cloneAndResolve(beads.Repo)
    default:
        return filepath.Join(rigPath, beads.Repo), nil
    }
}
```

## Backwards Compatibility

If `beads` section missing, assume `"repo": "local"`.