feat(v1): add temporal fall state machine

docs/07-v1-implementation-plan.md

@@ -293,7 +293,7 @@ git commit -m "feat(v1): add pose quality evidence"
 - Create: `v1/fall_state.py`
 - Create: `v1/tests/test_fall_state.py`
 
-- [ ] **Step 1: Write event timing tests**
+- [x] **Step 1: Write event timing tests**
 
 ```python
 def test_confirmed_event_is_emitted_once_after_persistence():
@@ -318,12 +318,12 @@ def test_confirmed_person_recovers_before_new_event_is_allowed():
     assert machine.state_of("7") is FallState.NORMAL
 ```
 
-- [ ] **Step 2: Run tests to verify failure**
+- [x] **Step 2: Run tests to verify failure**
 
 Run: `python -m pytest v1/tests/test_fall_state.py -v`
 Expected: FAIL because `FallStateMachine` is missing.
 
-- [ ] **Step 3: Implement the four-state contract**
+- [x] **Step 3: Implement the four-state contract**
 
 ```python
 from dataclasses import dataclass
@@ -399,12 +399,12 @@ class FallStateMachine:
 
 Use per-ID state, not global `frame_has_fall`. A source error and a rejected pose must not advance the machine.
 
-- [ ] **Step 4: Run tests**
+- [x] **Step 4: Run tests**
 
 Run: `python -m pytest v1/tests/test_fall_state.py -v`
 Expected: PASS.
 
-- [ ] **Step 5: Commit**
+- [x] **Step 5: Commit**
 
 ```powershell
 git add v1/fall_state.py v1/tests/test_fall_state.py docs progress.md