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/scripts/protocol/protocol.gd

@@ -12,7 +12,8 @@ extends Node
 ## Protocol version — must match server PROTOCOL_VERSION in bridge/types.rs.
 ## Reject snapshots where version != this value.
 ## v20: adds settings_response field to ObserverSnapshot (#627, D-138).
-const PROTOCOL_VERSION: int = 20
+## v21: adds economy_snapshot field to ObserverSnapshot (#822, D-181).
+const PROTOCOL_VERSION: int = 21
 
 # -- Decode: bytes from server → GDScript types --------------------------------