refactor: remove Gas Town references from codebase

Replace Gas Town-specific terminology with generic orchestrator concepts:
- "Gas Town" → "orchestrator" or "multi-clone"
- Hardcoded ~/gt/ paths → GT_ROOT environment variable
- signalGasTownActivity → signalOrchestratorActivity
- GUPP → hook-based work assignment

Updated 21 files across CHANGELOG, cmd/bd/, internal/, docs/, scripts.

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

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

Executed-By: beads/crew/dave
Rig: beads
Role: crew

cmd/bd/info.go

@@ -307,7 +307,7 @@ var versionChanges = []VersionChange{
 			"NEW: bd human command - Focused help menu for humans",
 			"NEW: bd show --short - Compact output mode for scripting",
 			"NEW: bd delete --reason - Audit trail for deletions",
-			"NEW: 'hooked' status - GUPP work assignment for Gas Town",
+			"NEW: 'hooked' status - Hook-based work assignment for orchestrators",
 			"NEW: mol_type schema field - Molecule classification tracking",
 			"FIX: --var flag allows commas in values (GH#786)",
 			"FIX: bd sync in bare repo worktrees (GH#785)",
@@ -327,7 +327,7 @@ var versionChanges = []VersionChange{
 			"NEW: bd where command - Show active beads location after following redirects",
 			"NEW: --parent flag for bd update - Reparent issues between epics",
 			"NEW: Redirect info in bd prime - Shows when database is redirected",
-			"FIX: bd doctor follows redirects - Gas Town compatibility",
+			"FIX: bd doctor follows redirects - Multi-clone compatibility",
 			"FIX: Remove 8-char prefix limit - bd rename-prefix allows longer prefixes",
 			"CHANGED: Git context consolidation - Internal refactor for efficiency",
 			"DOCS: Database Redirects section - ADVANCED.md documentation",