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/polecat_cycle_test.go

@@ -13,15 +13,15 @@ func TestParsePolecatSessionName(t *testing.T) {
 		// Valid polecat sessions
 		{
 			name:        "simple polecat",
-			sessionName: "gt-gastown-Toast",
-			wantRig:     "gastown",
+			sessionName: "gt-greenplace-Toast",
+			wantRig:     "greenplace",
 			wantPolecat: "Toast",
 			wantOk:      true,
 		},
 		{
 			name:        "another polecat",
-			sessionName: "gt-gastown-Nux",
-			wantRig:     "gastown",
+			sessionName: "gt-greenplace-Nux",
+			wantRig:     "greenplace",
 			wantPolecat: "Nux",
 			wantOk:      true,
 		},
@@ -34,8 +34,8 @@ func TestParsePolecatSessionName(t *testing.T) {
 		},
 		{
 			name:        "polecat with hyphen in name",
-			sessionName: "gt-gastown-Max-01",
-			wantRig:     "gastown",
+			sessionName: "gt-greenplace-Max-01",
+			wantRig:     "greenplace",
 			wantPolecat: "Max-01",
 			wantOk:      true,
 		},
@@ -43,21 +43,21 @@ func TestParsePolecatSessionName(t *testing.T) {
 		// Not polecat sessions (should return false)
 		{
 			name:        "crew session",
-			sessionName: "gt-gastown-crew-jack",
+			sessionName: "gt-greenplace-crew-jack",
 			wantRig:     "",
 			wantPolecat: "",
 			wantOk:      false,
 		},
 		{
 			name:        "witness session",
-			sessionName: "gt-gastown-witness",
+			sessionName: "gt-greenplace-witness",
 			wantRig:     "",
 			wantPolecat: "",
 			wantOk:      false,
 		},
 		{
 			name:        "refinery session",
-			sessionName: "gt-gastown-refinery",
+			sessionName: "gt-greenplace-refinery",
 			wantRig:     "",
 			wantPolecat: "",
 			wantOk:      false,
@@ -99,7 +99,7 @@ func TestParsePolecatSessionName(t *testing.T) {
 		},
 		{
 			name:        "no name after rig",
-			sessionName: "gt-gastown-",
+			sessionName: "gt-greenplace-",
 			wantRig:     "",
 			wantPolecat: "",
 			wantOk:      false,