docs: Remove remaining gt spawn references (gt-1py3y)

Update README.md, mayor.md.tmpl, and formula docs to use gt sling.

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

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

.beads/formulas/mol-town-shutdown.formula.toml

@@ -193,6 +193,6 @@ The daemon will:
 - Watch for pending spawns
 - Resume background coordination
 
-Polecats are NOT auto-respawned. Use `gt spawn` or let Witness
+Polecats are NOT auto-respawned. Use `gt sling` or let Witness
 restart them based on their preserved hooks.
 """

README.md

@@ -49,8 +49,8 @@ gt install ~/gt
 # Add a project rig
 gt rig add myproject --remote=https://github.com/you/myproject.git
 
-# Spawn a worker on an issue
-gt spawn --issue myproject-123
+# Assign work to a polecat
+gt sling myproject-123 myproject
 ```
 
 ## Architecture
@@ -81,7 +81,7 @@ Some of these are implemented; others are still aspirational. See docs for curre
 ```bash
 gt status             # Town status
 gt rig list           # List rigs
-gt spawn --issue <id> # Start worker
+gt sling <bead> <rig> # Assign work to polecat
 gt mail inbox         # Check messages
 gt peek <worker>      # Check worker health
 gt nudge <worker>     # Wake stuck worker

internal/templates/roles/mayor.md.tmpl

@@ -101,7 +101,7 @@ Town ({{ .TownRoot }})
 ### Work Management
 - `bd ready` - Issues ready to work (no blockers)
 - `bd list --status=open` - All open issues
-- `gt spawn --issue <id> --molecule <mol>` - Spawn polecat with molecule workflow
+- `gt sling <bead> <rig>` - Assign work to polecat in rig
 
 ### Delegation
 Prefer delegating to Refineries, not directly to polecats: