fix(client): post-sprint polish — protocol v21, schedule workaround, UI fixes

- Bump client protocol version 20 → 21 to match server (#822)
- Fix render_priority parameter name (was _render_priority, unused prefix)
- Fix debug console type inference (var sub := → var sub: String =)
- Economics panel: add population row, improve key hint text
- Stance indicator: hide on gameplay_occluded (D-170 fullscreen apps)
- Remove 5 broken clothing items from manifest and delete their GLBs
  (boots_work, coveralls_basic, jacket_utility, pants_cargo, shirt_henley)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

client/ui/debug_console.gd

@@ -248,7 +248,7 @@ func _dispatch_econ(parts: Array) -> void:
 			ERROR_COLOR,
 		)
 		return
-	var sub := parts[1].to_lower()
+	var sub: String = parts[1].to_lower()
 	match sub:
 		"inject":
 			_econ_inject(parts)