Replace 'gastown' with 'greenplace' in user-facing docs/examples

Using "greenplace" (The Green Place from Mad Max: Fury Road) as the
canonical example project/rig name in documentation and help text.
This provides a clearer distinction from the actual gastown repo name.

Changes:
- docs/*.md: Updated all example paths and commands
- internal/cmd/*.go: Updated help text examples
- internal/templates/: Updated example references
- Tests: Updated to use greenplace in example session names

Note: Import paths (github.com/steveyegge/gastown) and actual code
paths referencing the gastown repo structure are unchanged.

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

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

internal/cmd/refinery.go

@@ -42,8 +42,8 @@ and merges them to the appropriate target branches.
 If rig is not specified, infers it from the current directory.
 
 Examples:
-  gt refinery start gastown
-  gt refinery start gastown --foreground
+  gt refinery start greenplace
+  gt refinery start greenplace --foreground
   gt refinery start              # infer rig from cwd`,
 	Args: cobra.MaximumNArgs(1),
 	RunE: runRefineryStart,
@@ -93,7 +93,7 @@ or manual intervention.
 If rig is not specified, infers it from the current directory.
 
 Examples:
-  gt refinery attach gastown
+  gt refinery attach greenplace
   gt refinery attach          # infer rig from cwd`,
 	Args: cobra.MaximumNArgs(1),
 	RunE: runRefineryAttach,
@@ -108,7 +108,7 @@ Stops the current session (if running) and starts a fresh one.
 If rig is not specified, infers it from the current directory.
 
 Examples:
-  gt refinery restart gastown
+  gt refinery restart greenplace
   gt refinery restart          # infer rig from cwd`,
 	Args: cobra.MaximumNArgs(1),
 	RunE: runRefineryRestart,