feat: Remove gt spawn completely - gt sling is THE command (gt-1py3y)

Fully remove gt spawn from the codebase:

- Delete spawn.go, create polecat_spawn.go with just sling helpers
- Remove all gt spawn references from docs and CLAUDE.md
- Update code comments to reference gt sling

gt sling now handles ALL work dispatch:
- Existing agents: gt sling <bead> mayor/crew/witness
- Auto-spawn: gt sling <bead> <rig>
- No-tmux: gt sling <bead> <rig> --naked
- With args: gt sling <bead> --args "..."

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

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

docs/architecture.md

@@ -699,7 +699,7 @@ pending → in_progress → completed
 When a molecule is attached to an issue:
 
 ```bash
-gt spawn --issue gt-xyz --molecule mol-shiny
+gt sling gt-xyz <rig> --molecule mol-shiny
 ```
 
 1. Molecule is validated (steps, dependencies)
@@ -756,7 +756,7 @@ bd mol show mol-shiny
 bd mol bond mol-shiny --var feature_name="auth"
 
 # Spawn polecat with molecule
-gt spawn --issue gt-xyz --molecule mol-shiny
+gt sling gt-xyz <rig> --molecule mol-shiny
 ```
 
 ### Why Molecules?
@@ -1957,7 +1957,7 @@ gt capture <polecat> "<cmd>"     # Run command in polecat session
 ### Session Management
 
 ```bash
-gt spawn --issue <id> --molecule mol-shiny  # Spawn polecat with workflow
+gt sling <id> <rig> --molecule mol-shiny  # Spawn polecat with workflow
 gt handoff             # Polecat requests shutdown (run when done)
 gt session stop <p>    # Kill polecat session (Witness uses this)
 ```

docs/bootstrap.md

@@ -221,4 +221,4 @@ echo "Bootstrap complete!"
 After bootstrapping:
 1. Start a Mayor session: `gt mayor attach`
 2. Check for work: `bd ready`
-3. Spawn workers with molecules: `gt spawn --issue <id> --molecule mol-shiny`
+3. Spawn workers with molecules: `gt sling <id> <rig> --molecule mol-shiny`

docs/cross-project-deps.md

@@ -127,7 +127,7 @@ bd list --has-external-block
 
 **Manual (launch):**
 ```bash
-gt spawn --continue gt-mol-root
+gt sling gt-mol-root
 # Spawns polecat, which reads handoff mail and continues
 ```
 
@@ -153,7 +153,7 @@ Deacon patrol checks parked molecules:
 ### Phase 2: Gas Town Integration (gt-* issues)
 
 1. **gt park command**: Set blocked_by, clear assignee, handoff, shutdown
-2. **gt spawn --continue**: Resume parked molecule
+2. **gt sling**: Resume parked molecule
 3. **Patrol step**: Check parked molecules for unblocked
 
 ### Phase 3: Automation (future)
@@ -213,7 +213,7 @@ gt park --step=gt-mol.3 --waiting="beads:mol-run-assignee"
 # Polecat shutting down.
 
 # Later, after beads ships:
-gt spawn --continue gt-mol-root
+gt sling gt-mol-root
 # Resuming molecule gt-mol-root...
 # Reading handoff context...
 # Continuing from step gt-mol.3

docs/deacon-plugins.md

@@ -267,7 +267,7 @@ Execute registered plugins whose gates are open.
 ## Limitations
 
 - **No polecat spawning**: Plugins cannot spawn polecats. If a plugin tries
-  to use `gt spawn`, behavior is undefined. This may change in the future.
+  to use `gt sling`, behavior is undefined. This may change in the future.
 
 - **No cross-plugin dependencies**: Plugins don't declare dependencies on
   each other. If ordering matters, mark both as `parallel: false`.

docs/design/account-management.md

@@ -63,7 +63,7 @@ Highest priority override. Set this to use a specific account:
 
 ```bash
 export GT_ACCOUNT=yegge
-gt spawn gastown  # Uses yegge account
+gt sling <bead> gastown  # Uses yegge account
 ```
 
 ### Command Interface
@@ -100,13 +100,13 @@ gt account status
 
 ```bash
 # Override for a specific spawn
-gt spawn --account=yegge gastown
+gt sling <bead> gastown --account=yegge
 
 # Override for crew attach
 gt crew at --account=ghosttrack max
 
 # With env var (highest precedence)
-GT_ACCOUNT=yegge gt spawn gastown
+GT_ACCOUNT=yegge gt sling <bead> gastown
 ```
 
 ### Implementation Details
@@ -119,7 +119,7 @@ GT_ACCOUNT=yegge gt spawn gastown
 
 #### How Spawning Works
 
-When `gt spawn` or `gt crew at` runs Claude Code:
+When `gt sling` or `gt crew at` runs Claude Code:
 
 ```go
 func resolveAccountConfigDir() string {

docs/prompts.md

@@ -426,7 +426,7 @@ Unlike polecats, crew workers have no Witness oversight:
 ### Phase 3: Spawn & Lifecycle
 1. Port spawn injection prompts
 2. Add lifecycle templates (nudge, escalation)
-3. Integrate with `gt spawn` command
+3. Integrate with `gt sling` command
 
 ### Phase 4: CLI & Validation
 1. Implement `gt prime` with role detection

docs/vision.md

@@ -361,7 +361,7 @@ Putting it all together:
 
 ```
 1. Human files issue in Beads
-2. Mayor dispatches: gt spawn --issue <id>
+2. Mayor dispatches: gt sling --issue <id>
 3. Polecat created with:
    - Fresh worktree
    - mol-polecat-work pinned to hook