Update worklog with tier-up fix

worklog.md

@@ -650,6 +650,12 @@ Work Log:
   - Updated type definition in GameStore interface
   - Updated SkillsTab.tsx to pass `upgradeDialogMilestone` when committing
 
+- **Fixed tier-up upgrade reset in tierUpSkill()**:
+  - Root cause: `tierUpSkill()` was setting new tier's upgrades to empty array `[]`
+  - When tiering up, all previous tier's upgrades were lost
+  - Now copies current tier's upgrades to the new tier
+  - Example: Tier 1's L5/L10 upgrades persist when becoming Tier 2
+
 - **Added summoned golems display to SpireTab**:
   - Imported GOLEMS_DEF and helper functions
   - Added Mountain icon import
@@ -660,6 +666,7 @@ Work Log:
 
 Stage Summary:
 - Level 5 and level 10 upgrades no longer reset each other
-- Players can safely select upgrades at both milestones
+- Upgrades now carry over when tiering up to the next tier
+- Players can safely select upgrades at both milestones across all tiers
 - Summoned golems now visible in Spire tab during combat
-- Lint passes, dev server running
+- Lint passes, pushed to git (e2671d7)