docs(07-01): complete weight unit core plan

- SUMMARY.md with TDD results and 21-test coverage
- STATE.md updated to Plan 2 of 2, 17% progress
- ROADMAP.md marks 07-01 complete (1/2 plans)
- REQUIREMENTS.md marks UNIT-02, UNIT-03 complete

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

.planning/STATE.md

@@ -2,16 +2,16 @@
 gsd_state_version: 1.0
 milestone: v1.2
 milestone_name: Collection Power-Ups
-status: planning
-stopped_at: Phase 7 context gathered
-last_updated: "2026-03-16T10:56:52.192Z"
-last_activity: 2026-03-16 -- Roadmap created for v1.2
+status: executing
+stopped_at: Completed 07-01-PLAN.md
+last_updated: "2026-03-16T11:16:30Z"
+last_activity: 2026-03-16 -- Completed 07-01 weight unit core (formatWeight + useWeightUnit)
 progress:
   total_phases: 3
   completed_phases: 0
-  total_plans: 0
-  completed_plans: 0
-  percent: 0
+  total_plans: 2
+  completed_plans: 1
+  percent: 17
 ---
 
 # Project State
@@ -26,11 +26,11 @@ See: .planning/PROJECT.md (updated 2026-03-16)
 ## Current Position
 
 Phase: 7 of 9 (Weight Unit Selection)
-Plan: --
-Status: Ready to plan
-Last activity: 2026-03-16 -- Roadmap created for v1.2
+Plan: 2 of 2
+Status: Executing
+Last activity: 2026-03-16 -- Completed 07-01 weight unit core (formatWeight + useWeightUnit)
 
-Progress: [░░░░░░░░░░] 0%
+Progress: [█░░░░░░░░░] 17%
 
 ## Accumulated Context
 
@@ -42,6 +42,8 @@ Progress: [░░░░░░░░░░] 0%
 - Weight unit selection must be Phase 7 (formatWeight refactor touches all weight displays)
 - Classification belongs on setup_items join table, NOT items table
 - Candidate status and classification schema migrations in separate phases (sequential)
+- Weight conversion precision: g=0dp, oz=1dp, lb=2dp, kg=2dp
+- useWeightUnit validates stored value against known units to protect against corrupt data
 
 ### Pending Todos
 
@@ -53,6 +55,6 @@ None active.
 
 ## Session Continuity
 
-Last session: 2026-03-16T10:56:52.191Z
-Stopped at: Phase 7 context gathered
-Resume file: .planning/phases/07-weight-unit-selection/07-CONTEXT.md
+Last session: 2026-03-16T11:16:30Z
+Stopped at: Completed 07-01-PLAN.md
+Resume file: .planning/phases/07-weight-unit-selection/07-02-PLAN.md