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/assets/characters/clothing/boots_work/coverage.json

@@ -1,9 +0,0 @@
-{
-  "hides": [
-    "foot_l",
-    "foot_r",
-    "leg_lower_l",
-    "leg_lower_r"
-  ],
-  "torso_variant": "full"
-}

client/assets/characters/clothing/coveralls_basic/coverage.json

@@ -1,19 +0,0 @@
-{
-  "hides": [
-    "torso",
-    "hips",
-    "arm_upper_l",
-    "arm_upper_r",
-    "arm_lower_l",
-    "arm_lower_r",
-    "hand_l",
-    "hand_r",
-    "leg_upper_l",
-    "leg_upper_r",
-    "leg_lower_l",
-    "leg_lower_r",
-    "foot_l",
-    "foot_r"
-  ],
-  "torso_variant": "full"
-}