fix: address final-review findings (TopBar hydration, snapshot test, armor doc, inventory refresh test)

Fixes 4 Important findings from the final whole-branch review:
- /inventory never called WorldStore.load(), leaving the TopBar stuck on
  "loading" and characterLevel() silently defaulting to 1 for any character
  above level 1. Mirrors the same guard already used in HuntPageComponent.
- The combat/equipment snapshot-immutability integration test asserted only
  status/round, never the actual playerState snapshot the whole test claims
  to prove is untouched after a post-fight equip.
- Documented (comment only, no behavior change) that the demo character's
  armor dropping from the old hardcoded 6 to 0 is an intentional,
  spec-sanctioned tradeoff (Slice 0.5 spec Section19), not a bug.
- inventory.store.spec.ts's equip test used an identical inventory fixture
  before and after equip(), so a regression dropping the post-equip
  inventory re-fetch would still have passed. Now asserts the refetched
  fixture is actually reflected.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/database/seeds/vertical-slice.seed.ts

@@ -217,6 +217,13 @@ export async function seedVisibleVerticalSlice(
   const characterItemRepository = dataSource.getRepository(CharacterItem);
   const characterEquipmentRepository = dataSource.getRepository(CharacterEquipment);
 
+  // Starting loadout is weapon-only -- no starter armor piece exists in
+  // content yet -- so the demo character's effective armor (sum of equipped
+  // bonusArmor) is 0 until the player loots and equips bandit-hood (+3
+  // armor). This is a deliberate tradeoff, not a bug: Slice 0.5 spec §19
+  // says to preserve the existing demo balance "as closely as the
+  // implemented content allows" and explicitly forbids fabricating a full
+  // starter gear set just to hit the old hardcoded TEMPORARY_ARMOR = 6.
   const existingStartingSword = await characterItemRepository.findOneBy({
     characterId: DEMO_CHARACTER_ID,
     itemDefinitionId: ITEM_IDS['worn-short-sword'],