ux: add resource trend indicators

[itsmiso-ai]

Add small trend indicators for wood, stone, and food so players can understand whether the colony is gaining, stable, or losing resources.

This is especially important for food once worker upkeep from #133 exists.

Suggested display:

• Wood 7 ↑
• Stone 2 →
• Food 4 ↓

Keep the trend calculation simple and legible. Avoid graphs, history panels, or large management UI.

Acceptance Criteria

• Resource counters can show rising/stable/falling state.
• Food trend accounts for upkeep once design: increase worker cap through food and housing tradeoffs #133 lands, or is designed to support it later.
• Trend display works in bottom and side dock layouts.
• Add/extend layout tests so indicators do not clip.
• Add tests for trend calculation if implemented as pure logic.

[itsmiso-ai]

Saffron backlog grooming note

Applied by Saffron groomer.

Recommendation: ready
Lane: normal
Confidence: high

Reason: Well-scoped UX enhancement with explicit UI examples, clear acceptance criteria, test requirements, and graceful handling of a future dependency.

Summary

Add simple ↑/→/↓ trend indicators to wood, stone, and food resource counters. Implement pure logic for trend calculation, ensure compatibility with bottom/side dock layouts, add layout tests to prevent clipping, and design food trend logic to support future worker upkeep from #133.

Likely files / areas

• src/ui/resource-counters
• src/logic/trend-calculator
• tests/layout/

Acceptance criteria

• Resource counters display ↑, →, or ↓ based on recent resource changes.
• Food trend logic is extensible/hooked to support future worker upkeep from design: increase worker cap through food and housing tradeoffs #133.
• Indicators render correctly in both bottom and side dock layouts without clipping.
• Layout tests verify indicator positioning and sizing across dock configurations.
• Unit tests cover pure trend calculation logic.

Validation

• npm run test -- --testPathPattern='trend|layout' && npm run lint

Next action

Implement the pure trend calculation logic with unit tests first, then integrate into resource counter components. Verify rendering in both dock layouts and run layout tests to catch clipping early.