[AZ-599] Batch 79: FT-P-02 Derkachi builder + _common.py extraction

- Add build_p02_fixtures.py: IMU CSV → tlog conversion (RAW_IMU +
  ATTITUDE pairs, centidegrees→radians yaw) and orchestrator that
  runs gps-denied replay against Derkachi MP4 + generated tlog,
  verifying ≥1 record_type="estimate" in the FDR archive.
- Extract run_gps_denied_replay + FDR-parent-dir helpers into
  sitl_replay_builder/_common.py; refactor build_p01_fixtures.py
  to import from _common (b78 tests preserved).
- Add 20 unit tests under e2e/_unit_tests/fixtures/test_sitl_
  replay_builder_p02.py covering AC-1..AC-5; total unit suite
  686/686 passing (regression gate AC-6).
- README updated to document FT-P-01 + FT-P-02 builders.
- Advance autodev state: last_completed_batch=79, current_batch=80;
  prune verbose detail blob.

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/_autodev_state.md

@@ -6,16 +6,16 @@ step: 10
 name: Implement Tests
 status: in_progress
 sub_step:
-  phase: 6
-  name: implement-tasks-sequentially
+  phase: 0
+  name: awaiting-invocation
   detail: ""
 retry_count: 0
 cycle: 1
 tracker: jira
-last_completed_batch: 78
+last_completed_batch: 79
 last_cumulative_review: batches_76-78
-current_batch: 79
-current_batch_tasks: ""
+current_batch: 80
+
 last_step_outcomes:
   step_8: "Code is testable — no changes needed (testability_assessment.md committed; no list-of-changes, no source edits)"
-  step_9: "Already complete — 41 blackbox test tasks (AZ-406..AZ-446) under epic AZ-262 with specs in _docs/02_tasks/todo/ were produced in a prior cycle; AZ-406 test-infrastructure bootstrap also pre-existing. Folder fallback satisfied (todo/ has test tasks, _dependencies_table.md reflects 114 product + 41 test = 155 total). No Step-9 work executed in cycle 1."
+  step_9: "41 blackbox test tasks (AZ-406..AZ-446) under epic AZ-262 in _docs/02_tasks/todo/ pre-existing; AZ-406 test-infra bootstrap pre-existing. Folder fallback satisfied. No Step-9 work executed in cycle 1."