chore: complete v1.1 milestone

Archive v1.1 Calendar & Polish milestone artifacts (roadmap,
requirements, phase directories) to milestones/. Evolve PROJECT.md
with validated requirements and new key decisions. Update
RETROSPECTIVE.md with v1.1 section and cross-milestone trends.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.planning/RETROSPECTIVE.md

@@ -46,6 +46,50 @@
 
 ---
 
+## Milestone: v1.1 — Calendar & Polish
+
+**Shipped:** 2026-03-16
+**Phases:** 3 | **Plans:** 5
+
+### What Was Built
+- Horizontal 181-day calendar strip replacing the stacked daily plan HomeScreen
+- CalendarDao with date-parameterized reactive Drift streams for day tasks and overdue tasks
+- Task completion history bottom sheet with per-task reverse-chronological log
+- Alphabetical, interval, and effort sort options with SharedPreferences persistence
+- SortDropdown widget in both HomeScreen and TaskListScreen AppBars
+
+### What Worked
+- Phase dependency ordering (5 → 6+7 parallel-capable) meant calendar strip was stable before building features on top
+- TDD red-green cycle continued smoothly — every plan had failing tests before implementation
+- Auto-advance mode enabled rapid phase chaining with minimal manual intervention
+- Existing patterns from v1.0 (DAO, provider, widget test) were reused directly — no new patterns invented unnecessarily
+- CalendarStripController (VoidCallback holder) was simpler than GlobalKey approach — good architecture call
+
+### What Was Inefficient
+- StateProvider removal in Riverpod 3.x was discovered during execution rather than research — same category of issue as v1.0's riverpod_generator problem
+- ROADMAP.md plan checkboxes still not auto-checked by executor (same bookkeeping gap as v1.0)
+- Phase 5 plan split (data layer + UI) could have been a single plan given the small scope — overhead of 2 separate plans wasn't justified for ~13 min total
+
+### Patterns Established
+- CalendarStripController: VoidCallback holder for parent-to-child imperative scroll communication
+- CalendarDayList state machine: first-run → celebration → emptyDay → hasTasks (5 states)
+- In-memory sort via stream.map after DB stream emit — sort preference changes without re-querying
+- SortPreferenceNotifier: sync default + async _loadPersisted() — matches ThemeNotifier pattern
+- Nested Scaffold pattern for per-tab AppBars in StatefulShellRoute.indexedStack
+
+### Key Lessons
+1. Riverpod API surface changes (StateProvider removal) should be caught during phase research, not during execution — pattern repeats from v1.0
+2. Plans under ~5 min execution can be merged into a single plan to reduce orchestration overhead
+3. In-memory sort is the right approach when sort criteria don't affect DB queries — avoids re-streaming
+4. Bottom sheets for one-shot modals (history) don't need dedicated Riverpod providers — ref.read() in ConsumerWidget is sufficient
+
+### Cost Observations
+- Model mix: orchestrator on opus, executors/checkers on sonnet
+- Total execution: ~26 min for 5 plans across 3 phases
+- Notable: Each plan averaged ~5 min — significantly faster than v1.0's ~6 min average due to established patterns
+
+---
+
 ## Cross-Milestone Trends
 
 ### Process Evolution
@@ -53,13 +97,17 @@
 | Milestone | Phases | Plans | Key Change |
 |-----------|--------|-------|------------|
 | v1.0 | 4 | 13 | Initial project — established all patterns |
+| v1.1 | 3 | 5 | Reused v1.0 patterns — faster execution, auto-advance mode |
 
 ### Cumulative Quality
 
-| Milestone | Tests | Key Metric |
-|-----------|-------|------------|
-| v1.0 | 89 | dart analyze clean, 0 issues |
+| Milestone | Tests | LOC (lib) | Key Metric |
+|-----------|-------|-----------|------------|
+| v1.0 | 89 | 7,773 | dart analyze clean, 0 issues |
+| v1.1 | 108 | 9,051 | dart analyze clean, 0 issues |
 
 ### Top Lessons (Verified Across Milestones)
 
-1. (Single milestone — lessons above will be cross-validated as more milestones ship)
+1. **Research must verify current package API signatures** — v1.0 hit riverpod_generator type incompatibility, v1.1 hit StateProvider removal. Same root cause: outdated API assumptions in plans.
+2. **Established patterns compound** — v1.1 plans averaged ~5 min vs v1.0's ~6 min. Reusing DAO, provider, and test patterns eliminated design decisions.
+3. **Verification gates are cheap insurance** — Consistently ~2 min per phase, caught regressions in both milestones.