[autodev] Step 13 partial: helpers 1-4 cycle-1 doc sync

Batch 5a of the cycle-1 doc sync. For each of the four
foundation helpers (imu_preintegrator, se3_utils,
lightglue_runtime, wgs_converter):

- Append "Cycle-1 operational reality" section to the
  existing common-helpers/<NN>_*.md, documenting what the
  shipped implementation actually exposes vs. the design-
  intent sketch (interfaces, exception types, public
  constants, AZ-task lineage).

Specific cycle-1 facts captured per helper:

- imu_preintegrator (AZ-276): make_imu_preintegrator
  factory, BMI088-class noise defaults, single
  ImuPreintegrationError exception, actual return type is
  PreintegratedCombinedMeasurements (consumer builds the
  CombinedImuFactor), destructive reset_with_bias semantics,
  first-sample-not-integrated dt=0 handling.
- se3_utils (AZ-277): SE3 = gtsam.Pose3 re-export,
  Se3InvalidMatrixError, strict caller-orthogonalisation
  invariant, _DEFAULT_ROT_ATOL=1e-6 and small-angle Taylor
  cutoff for exp_map, is_valid_rotation predicate, strict
  dtype=float64 everywhere.
- lightglue_runtime (AZ-278 / R14 fix): EngineHandle
  Protocol-typed constructor, LightGlueRuntimeError +
  LightGlueConcurrentAccessError, non-blocking concurrent-
  access guard (raises rather than serialises),
  match_batch equal-length precondition, composition-root
  single-instance into C2.5 + C3.
- wgs_converter (AZ-279 + AZ-490): WEB_MERCATOR_MAX_LAT_DEG
  and MAX_ZOOM constants, WgsConversionError, ECEF arrays
  are ndarray(3,) float64, new horizontal_distance_m method
  (AZ-490 takeoff-origin bounded-delta gate), slippy-map
  tile math hand-rolled to match satellite-provider on-disk
  layout.

Two contract files (imu_preintegrator.md and
wgs_converter.md) need follow-up minor revisions to match
shipped surface; queued for the next contracts-folder
sweep, noted inline in each helper's new section.

Also refresh D-CROSS-CVE-1 opencv-pin leftover replay
timestamp (8-min debounce — gtsam upstream state cannot
change in that window).

Bumps _docs/_autodev_state.md sub_step detail.

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

_docs/02_document/common-helpers/04_helper_wgs_converter.md

@@ -41,3 +41,19 @@ class WgsConverter:
 
 - The static-only design satisfies the coderule.mdc constraint ("only use static methods for pure self-contained computations"). If a future deployment needs alternative datum support, switch to an instance-based factory then.
 - Tile-coordinate math is zoom-level-sensitive; callers MUST pass the right zoom level for the tile in question (typically zoomLevel from `TileMetadata`).
+
+## Cycle-1 operational reality
+
+The shipped surface in `src/gps_denied_onboard/helpers/wgs_converter.py` (AZ-279, extended by AZ-490) is the canonical entry point for every geodesy hop in the system. Stateless and `pyproj`-backed (`EPSG:4326 ↔ EPSG:4978`), with module-level `Transformer` instances cached on import.
+
+- **Public constants** — `WEB_MERCATOR_MAX_LAT_DEG = 85.0511287798066` (the slippy-map cutoff; outside this band, `latlon_to_tile_xy` raises) and `MAX_ZOOM = 22` (slippy-map upper bound; exposed so callers can validate operator input without hard-coding the limit).
+- **`WgsConversionError`** — single public exception type (subclasses `ValueError`). Raised on: non-finite `lat/lon/alt`; latitude/longitude out of WGS-84 range; non-`ndarray` or wrong-shape ECEF input; non-`float64` ECEF input; `zoom` not a non-bool `int` or out of `[0, MAX_ZOOM]`; tile `(x, y)` out of `[0, 2**zoom)`; latitude outside the Web-Mercator band for `latlon_to_tile_xy`.
+- **ECEF arrays are `np.ndarray` of shape `(3,)` and `dtype=float64`** — the Interface sketch above uses "Vector3" as a placeholder. `latlonalt_to_ecef` returns a freshly-allocated array; `ecef_to_latlonalt` and `local_enu_to_latlonalt` validate input shape/dtype and raise `WgsConversionError` on mismatch.
+- **`horizontal_distance_m(a: LatLonAlt, b: LatLonAlt) -> float`** — new method added in AZ-490 for C5's `set_takeoff_origin` bounded-delta gate. Computes the geodesic horizontal distance in metres via the same ECEF transformer used by `latlonalt_to_local_enu`: convert `b` into the local-ENU frame anchored at `a`, then `hypot(east, north)`. Altitude is ignored (flat-distance on the WGS-84 ellipsoid, NOT a 3-D distance). Accuracy ≤ sub-mm vs. Vincenty for separations ≤ a few km — the bounded-delta gate operates at ≤ ~1 km, so AZ-490's "geodesic horizontal distance" AC is satisfied.
+- **Slippy-map tile math** — hand-rolled (NOT `pyproj`) to match OSM's `{zoom}/{x}/{y}.jpg` convention byte-equal so files produced by `satellite-provider` round-trip exactly. `latlon_to_tile_xy` clamps the output into `[0, n-1]` after `floor` — out-of-band latitude is rejected before this clamp via the Web-Mercator range check. `tile_xy_to_latlon_bounds` returns a `BoundingBox(min_lat_deg, min_lon_deg, max_lat_deg, max_lon_deg)` matching the tile's outer extent.
+- **`pyproj` import** — `from pyproj import Transformer` is tagged `# type: ignore[import-not-found]` because `pyproj` ships type stubs in a separate package; the project pin does not add the stubs. Don't drop the ignore comment in mypy passes.
+
+### Cycle-1 task lineage
+
+- AZ-279 — initial helper, contract producer (`latlonalt_to_*`, `*_to_latlonalt`, `latlon_to_tile_xy`, `tile_xy_to_latlon_bounds`).
+- AZ-490 — `horizontal_distance_m` addition for C5's takeoff-origin bounded-delta gate. Contract minor revision (v1.0.0 → v1.1.0) is queued for the next contracts-folder sweep.