[AZ-332] C1 OKVIS2 Strategy: facade + binding skeleton

Python facade (`Okvis2Strategy`) is production-quality and satisfies
AZ-331's `VioStrategy` protocol; full AC-1..10 coverage with
AC-9 + NFR-perf marked `tier2`. The C++ pybind11 binding compiles
and loads but throws `OkvisFatalException("estimator not yet wired")`
on first `add_frame` — the `okvis::ThreadedKFVio` wiring is a tier2
follow-up the Step-15 Product Completeness Gate is expected to track
as a remediation task.

Resolved contradictions:

* Constructor signature aligned with the AZ-331 factory: `(config, *,
  fdr_client, clock=None)`. Calibration / preintegrator / logger
  built internally from config. No churn on AZ-331.
* IMU substrate: OKVIS2 owns its internal estimator IMU integration;
  the AZ-276 `ImuPreintegrator` is a separate substrate consumed by
  E-C5's fusion graph. Single source of truth lives at the sample
  stream, not the integrator instance.
* FDR API: `FdrClient.enqueue(record)` with new `vio.health` kind
  added to AZ-272 `KNOWN_PAYLOAD_KEYS`.

CI matrix forces `-DBUILD_OKVIS2=OFF` until the tier2 wiring task
brings Ceres / SuiteSparse / OKVIS2 vendored submodules into the
Linux build.

Files: 17 added/modified across `c1_vio/`, `fdr_client/records.py`,
`cpp/okvis2/CMakeLists.txt`, CI workflow, AZ-332 task spec
(implementation-notes section), batch 23 report.

Tests: 17 new (15 tier1 + 2 tier2). Full Tier-1 suite: 1109 pass,
2 skipped (env), 2 deselected (tier2). No regressions.

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

src/gps_denied_onboard/fdr_client/records.py

@@ -40,6 +40,13 @@ KNOWN_PAYLOAD_KEYS: Final[dict[str, frozenset[str]]] = {
     "vio.tick": frozenset(
         {"frame_id", "R", "t", "P", "last_anchor_age_ms", "mre_px", "imu_bias_norm"}
     ),
+    # AZ-332 / E-C1: emitted on every VioStrategy state transition
+    # (INIT->TRACKING->DEGRADED->LOST etc.). One record per transition;
+    # steady-state frames emit nothing on this kind. `frame_id` is the
+    # frame the transition was decided on (may be empty for INIT->...).
+    "vio.health": frozenset(
+        {"state", "consecutive_lost", "bias_norm", "strategy_label", "frame_id"}
+    ),
     "state.tick": frozenset({"frame_id", "fused_pose", "covariance_2x2", "estimator_label"}),
     "tile_match": frozenset({"frame_id", "tile_id", "score", "match_count", "ransac_inliers"}),
     "overrun": frozenset({"producer_id", "dropped_count"}),