plan: Phase 8 DAG System TDD with 2 plans

- 08-01: GameDAGRouter edge cases and anchor validation TDD (17+ tests)
- 08-02: Performance with large datasets (10K+ games) and diversity coverage TDD

TDD discipline: tests define correctness, code must match.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.planning/phases/08-dag-system-tdd/08-01-PLAN.md

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+---
+phase: 08-dag-system-tdd
+type: execute
+---
+
+<objective>
+TDD for GameDAGRouter edge cases and anchor game validation.
+
+Purpose: Ensure the DAG routing algorithm handles boundary conditions correctly before testing at scale.
+Output: Comprehensive edge case test suite for GameDAGRouter, with code fixes if tests fail.
+</objective>
+
+<execution_context>
+~/.claude/get-shit-done/workflows/execute-phase.md
+./summary.md
+~/.claude/get-shit-done/references/tdd.md
+</execution_context>
+
+<context>
+@.planning/PROJECT.md
+@.planning/ROADMAP.md
+@SportsTime/Planning/Engine/GameDAGRouter.swift
+@SportsTimeTests/ScenarioBPlannerTests.swift
+</context>
+
+<tasks>
+
+<task type="auto">
+  <name>Task 1: Create GameDAGRouterTests with edge case tests</name>
+  <files>SportsTimeTests/GameDAGRouterTests.swift</files>
+  <action>
+Create a new test file using Swift Testing framework (@Test attributes, #expect assertions).
+
+Include test helpers:
+- makeStadium(id:city:lat:lon:) with default coordinates spread across US
+- makeGame(id:stadiumId:startTime:) with default sport/teams
+- date(_:) helper for "yyyy-MM-dd HH:mm" parsing
+
+Write RED tests for these edge cases:
+1. Empty games array → returns empty routes
+2. Single game → returns [[game]] (unless anchor mismatch)
+3. Single game with non-matching anchor → returns []
+4. Two games, chronological and feasible → returns route containing both
+5. Two games, chronological but infeasible (too far) → returns two separate single-game routes
+6. Two games, reverse chronological (second before first) → returns two separate single-game routes
+7. Three games where only pairs are feasible → returns all valid pairs/singles
+8. Anchor game filtering: routes missing anchors are excluded
+9. Repeat cities OFF: routes with same city twice are excluded
+10. Repeat cities ON: routes with same city twice are included
+
+Run tests expecting failures for any code gaps:
+```bash
+xcodebuild -project SportsTime.xcodeproj -scheme SportsTime -destination 'platform=iOS Simulator,name=iPhone 17,OS=26.2' -only-testing:SportsTimeTests/GameDAGRouterTests test
+```
+  </action>
+  <verify>All edge case tests exist and execute (RED or GREEN)</verify>
+  <done>GameDAGRouterTests.swift contains 10+ edge case tests using Swift Testing framework</done>
+</task>
+
+<task type="auto">
+  <name>Task 2: Fix any failing edge case tests</name>
+  <files>SportsTime/Planning/Engine/GameDAGRouter.swift</files>
+  <action>
+Run the edge case tests. For any failures:
+1. Identify the exact assertion that fails
+2. Trace the code path in GameDAGRouter.swift
+3. Fix the logic bug (do NOT modify the test - tests define correctness)
+4. Re-run until GREEN
+
+Common fix areas:
+- Edge case handling in findRoutes() lines 101-120
+- canTransition() feasibility logic lines 463-507
+- Anchor filtering logic lines 181-184
+
+Do NOT change test expectations. If a test fails, the code is wrong.
+  </action>
+  <verify>
+```bash
+xcodebuild -project SportsTime.xcodeproj -scheme SportsTime -destination 'platform=iOS Simulator,name=iPhone 17,OS=26.2' -only-testing:SportsTimeTests/GameDAGRouterTests test
+```
+All tests pass
+  </verify>
+  <done>All 10+ edge case tests pass (GREEN)</done>
+</task>
+
+<task type="auto">
+  <name>Task 3: Add canTransition boundary tests</name>
+  <files>SportsTimeTests/GameDAGRouterTests.swift</files>
+  <action>
+Add tests for canTransition edge cases via findRoutes() behavior:
+
+1. Same stadium, same day, 4 hours apart → transition feasible
+2. Different stadium, 1000 miles apart, same day → infeasible (not enough driving time)
+3. Different stadium, 1000 miles apart, 2 days apart → feasible (enough driving days)
+4. Different stadium, 100 miles apart, 4 hours available → feasible
+5. Different stadium, 100 miles apart, 1 hour available → infeasible (need 3hr buffer after game)
+6. Game end buffer: 3hr buffer after game end before departure
+7. Arrival buffer: 1hr buffer before next game start
+
+These test the canTransition() logic indirectly through findRoutes() results.
+  </action>
+  <verify>
+```bash
+xcodebuild -project SportsTime.xcodeproj -scheme SportsTime -destination 'platform=iOS Simulator,name=iPhone 17,OS=26.2' -only-testing:SportsTimeTests/GameDAGRouterTests test
+```
+All tests pass
+  </verify>
+  <done>7 additional boundary tests pass (17+ total tests)</done>
+</task>
+
+</tasks>
+
+<verification>
+Before declaring phase complete:
+- [ ] `xcodebuild test` for GameDAGRouterTests passes with 17+ tests
+- [ ] All edge cases documented in test names
+- [ ] No tests were modified to pass (code was fixed instead)
+- [ ] Existing tests in other test files still pass
+</verification>
+
+<success_criteria>
+
+- All tasks completed
+- All verification checks pass
+- 17+ edge case tests for GameDAGRouter
+- TDD discipline maintained (tests define correctness)
+</success_criteria>
+
+<output>
+After completion, create `.planning/phases/08-dag-system-tdd/08-01-SUMMARY.md`
+</output>