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+---
+phase: 06-renderer-architecture
+plan: 01
+subsystem: ui
+tags: [typescript, d3, strategy-pattern, state-management]
+
+requires:
+  - phase: 01-05 (v1.0)
+    provides: heatmap.ts monolith with all rendering logic
+provides:
+  - ModeRenderer interface and RenderContext type contracts
+  - HeatmapState creation via createInitialState()
+  - Renderer registry (registerRenderer/getRenderer)
+  - Shared tooltip, color-scale, stats, date-utils modules
+affects: [06-02, 06-03, 07-mode-renderers]
+
+tech-stack:
+  added: []
+  patterns: [strategy-pattern renderer registry, state factory function, shared utility extraction]
+
+key-files:
+  created:
+    - assets/src/state.ts
+    - assets/src/renderers/types.ts
+    - assets/src/renderers/registry.ts
+    - assets/src/shared/tooltip.ts
+    - assets/src/shared/color-scale.ts
+    - assets/src/shared/stats.ts
+    - assets/src/shared/date-utils.ts
+    - assets/test/state.test.ts
+    - assets/test/registry.test.ts
+    - assets/test/tooltip.test.ts
+    - assets/test/color-scale.test.ts
+    - assets/test/date-utils.test.ts
+  modified:
+    - assets/src/types.ts
+
+key-decisions:
+  - "clearRegistry() exported for test isolation of module-level Map"
+  - "Tooltip consolidated: createTooltip now appends to body and sets fixed positioning (was scattered inline in heatmap.ts)"
+  - "FALLBACK_COLORS used directly in color-scale, resolveColors() dropped (always returned same value)"
+
+patterns-established:
+  - "Strategy pattern: ModeRenderer interface with mode string key, render(ctx), optional destroy()"
+  - "State factory: plain interface + createInitialState() function, no class"
+  - "Shared utilities: pure functions extracted to assets/src/shared/ with independent tests"
+
+requirements-completed: []
+
+duration: 2min
+completed: 2026-04-09
+---
+
+# Phase 6 Plan 01: Foundation Modules Summary
+
+**Strategy-pattern renderer contracts, state factory, registry, and 4 shared utility modules extracted from heatmap.ts monolith**
+
+## Performance
+
+- **Duration:** 2 min
+- **Started:** 2026-04-09T07:31:40Z
+- **Completed:** 2026-04-09T07:34:36Z
+- **Tasks:** 2
+- **Files modified:** 13
+
+## Accomplishments
+- Created ModeRenderer/RenderContext type contracts for strategy-pattern rendering
+- Built state module with HeatmapState interface and createInitialState() factory
+- Built renderer registry with register/get/clear operations
+- Extracted tooltip, color-scale, stats, and date-utils as standalone shared modules
+- All 62 tests pass (20 new + 42 existing), esbuild still produces valid output
+
+## Task Commits
+
+Each task was committed atomically:
+
+1. **Task 1: Create type contracts, state module, and renderer registry** - `fe24e8b` (feat)
+2. **Task 2: Extract shared utilities from heatmap.ts** - `b9b2565` (feat)
+
+## Files Created/Modified
+- `assets/src/types.ts` - Added DisplayMetric, HeatmapMode, FilterState types
+- `assets/src/state.ts` - HeatmapState interface and createInitialState() factory
+- `assets/src/renderers/types.ts` - ModeRenderer and RenderContext interfaces
+- `assets/src/renderers/registry.ts` - Renderer registration and lookup with clearRegistry()
+- `assets/src/shared/tooltip.ts` - Consolidated tooltip create/show/hide functions
+- `assets/src/shared/color-scale.ts` - buildColorScale with DisplayMetric support
+- `assets/src/shared/stats.ts` - calculateStreak, calculateStats, renderStats
+- `assets/src/shared/date-utils.ts` - buildDateMap, generateCells, getWeekInterval, DayCell
+- `assets/test/state.test.ts` - 2 tests for state factory
+- `assets/test/registry.test.ts` - 3 tests for registry
+- `assets/test/tooltip.test.ts` - 5 tests for tooltip lifecycle
+- `assets/test/color-scale.test.ts` - 4 tests for color scale
+- `assets/test/date-utils.test.ts` - 6 tests for date utilities
+
+## Decisions Made
+- clearRegistry() exported from registry.ts for test isolation (module-level Map needs clearing between tests)
+- Tooltip creation consolidated: new createTooltip() appends to body with fixed positioning (was scattered across multiple lines in heatmap.ts)
+- resolveColors() dropped from color-scale module -- it always returned FALLBACK_COLORS
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Issues Encountered
+None.
+
+## User Setup Required
+None - no external service configuration required.
+
+## Next Phase Readiness
+- All building blocks ready for Plan 02 to wire heatmap.ts to use shared modules
+- ModeRenderer interface ready for year-mode renderer implementation
+- State and registry ready for mode switching logic
+
+## Self-Check: PASSED
+
+- All 12 created files exist on disk
+- Both task commits verified (fe24e8b, b9b2565)
+- Full test suite: 62/62 passing
+- esbuild: produces valid output
+
+---
+*Phase: 06-renderer-architecture*
+*Completed: 2026-04-09*