[AZ-343] C2.5 InlierCountReRanker + shared FeatureExtractor helper

Implements the production-default ReRankStrategy: K=10 → N=3 by
single-pair LightGlue inlier count, with strict drop-and-continue
(INV-8) on per-candidate TileFetch / backbone / zero-inlier failures
and RerankAllCandidatesFailedError on zero survivors. Composition
root injects the shared LightGlueRuntime + Clock + the new
FeatureExtractor helper (an L1 placeholder OpenCvOrbExtractor that
unblocks AZ-343 and future C3 strategies — task scope expansion).

Architectural notes:
- Cross-component imports stay banned; tile_store types as `object`
  and the C6 TileCacheError family is duck-typed by class module
  prefix (same workaround AZ-348 adopted for c7_inference; proper
  fix is to relocate TileCacheError to _types/ in a follow-up).
- Clock injection follows the replay contract (AZ-398 Invariant 2);
  reranked_at is sourced from clock.monotonic_ns().
- AZ-342 factory grew `feature_extractor` + `clock` + `fdr_client`
  parameters; existing AZ-342 conformance tests updated.

Tests: 19 new AC-1..AC-12 + mixed-failure scenarios in
test_inlier_count_reranker.py; existing AZ-342 suite (26) still
green. Full repo sweep 1093 passed / 2 skipped (cmake/actionlint
not on PATH).

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

_docs/02_document/components/03_c2_5_rerank/description.md

@@ -4,11 +4,12 @@
 
 **Purpose**: re-rank C2's top-K=10 VPR candidates down to top-N=3 by single-pair LightGlue inlier count, producing a higher-precision input for the cross-domain matcher (C3). The re-rank step is the architectural boundary between cheap descriptor retrieval (C2) and expensive cross-domain matching (C3) — it pays a small extra cost so C3 only operates on the most promising candidates.
 
-**Architectural Pattern**: Strategy (single concrete implementation today: `InlierCountReRanker`). Future re-rank algorithms can be added as additional `ReRankStrategy` implementations behind the same interface.
+**Architectural Pattern**: Strategy (single concrete implementation today: `InlierCountReRanker`, AZ-343). Future re-rank algorithms can be added as additional `ReRankStrategy` implementations behind the same interface.
 
 **Upstream dependencies**:
 - C2 → `VprResult` (top-K=10 candidates).
 - Shared `LightGlueRuntime` helper (used in single-pair mode for inlier counting; the same matcher object is shared with C3 — owned by the helper, not by C3, so neither component depends on the other at build time).
+- Shared `FeatureExtractor` helper (`helpers/feature_extractor.py`, AZ-343 scope expansion) — extracts `KeypointSet` from both the per-frame nav image and each candidate's tile JPEG; the placeholder impl is `OpenCvOrbExtractor`, swapped out for a TRT-backed deep extractor before flight.
 - C6 TileStore → fetch tile pixels for each candidate (cheap, in-memory page-cache hit during a flight).
 - Camera calibration artifact — for nav-frame preprocessing.
 
@@ -59,7 +60,7 @@ No caching layer beyond C6's mmap. The same tile may be fetched repeatedly acros
 
 **Algorithmic Complexity**: `O(K)` LightGlue forward passes per frame (K=10), each `O(M_tile · M_query)` in feature counts. The whole step is GPU-bound on the same engine that C3 uses — hence the shared LightGlue runtime.
 
-**State Management**: stateless per-frame. Holds a reference to the shared LightGlue object owned by C3.
+**State Management**: stateless per-frame. Holds references to the constructor-injected `LightGlueRuntime`, `FeatureExtractor`, `TileStore`, `Clock`, and (optionally) `FdrClient` — all lifecycle-owned by the runtime root, not by C2.5.
 
 **Key Dependencies**:
 
@@ -78,6 +79,8 @@ No caching layer beyond C6's mmap. The same tile may be fetched repeatedly acros
 | Helper | Purpose | Used By |
 |--------|---------|---------|
 | `LightGlueRuntime` | shared LightGlue inference handle (one engine, many call sites) | C2.5, C3 |
+| `FeatureExtractor` (`helpers/feature_extractor.py`) | shared image → `KeypointSet` extractor; default `OpenCvOrbExtractor`, target TRT-backed DISK/ALIKED | C2.5, future C3 backbones |
+| `Clock` (`gps_denied_onboard.clock`) | composition-root time source; stamps `RerankResult.reranked_at` via `clock.monotonic_ns()` (Invariant 2 of the replay contract — no direct `time.*` in components) | every C* component |
 
 ## 7. Caveats & Edge Cases
 

_docs/02_document/module-layout.md

@@ -57,12 +57,14 @@ Bootstrap reference: `_docs/02_tasks/todo/AZ-263_initial_structure.md`. Architec
 - **Epic**: AZ-256 (E-C2.5 Rerank)
 - **Directory**: `src/gps_denied_onboard/components/c2_5_rerank/`
 - **Public API**:
-  - `__init__.py` (re-exports `ReRankStrategy`, `RerankResult`, `RerankCandidate`)
+  - `__init__.py` (re-exports `ReRankStrategy`, `RerankResult`, `RerankCandidate`, `RerankError` family, `C2_5RerankConfig`)
   - `interface.py` (`ReRankStrategy` Protocol)
+  - `config.py` (`C2_5RerankConfig` dataclass; registered on import; `strategy`, `top_n`, `debug_per_frame_log` fields)
+  - `errors.py` (`RerankError`, `RerankBackboneError`, `RerankAllCandidatesFailedError`)
 - **Internal**:
-  - `inlier_based_reranker.py` (single-pair LightGlue inlier count K=10→N=3)
-- **Owns**: `src/gps_denied_onboard/components/c2_5_rerank/**`, `tests/unit/c2_5_rerank/**`
-- **Imports from**: `_types`, `helpers.lightglue_runtime`, `helpers.descriptor_normaliser`, `helpers.ransac_filter`, `helpers.se3_utils`, `components.c6_tile_cache` (Public API), `components.c7_inference`, `config`, `logging`, `fdr_client`
+  - `inlier_based_reranker.py` (`InlierCountReRanker` — single-pair LightGlue inlier count K=10→N=3, AZ-343; module-level `create()` factory entry-point consumed by `runtime_root.rerank_factory.build_rerank_strategy`; gated by `BUILD_RERANK_INLIER_COUNT`)
+- **Owns**: `src/gps_denied_onboard/components/c2_5_rerank/**`, `src/gps_denied_onboard/runtime_root/rerank_factory.py`, `tests/unit/c2_5_rerank/**`
+- **Imports from**: `_types`, `helpers.lightglue_runtime`, `helpers.feature_extractor` (AZ-343 scope expansion), `helpers.descriptor_normaliser`, `helpers.ransac_filter`, `helpers.se3_utils`, `components.c6_tile_cache` (Public API only — `TileStore`, `TilePixelHandle`, `TileCacheError` family), `clock`, `config`, `logging`, `fdr_client`
 - **Consumed by**: `c3_matcher`, `runtime_root`
 
 ### Component: c3_matcher
@@ -289,6 +291,13 @@ Bootstrap reference: `_docs/02_tasks/todo/AZ-263_initial_structure.md`. Architec
 - **Owned by**: AZ-264.
 - **Consumed by**: c2_5_rerank, c3_matcher.
 
+### shared/helpers/feature_extractor
+
+- **Directory**: `src/gps_denied_onboard/helpers/feature_extractor.py`
+- **Purpose**: Shared image → `KeypointSet` Protocol + placeholder `OpenCvOrbExtractor` impl (AZ-343 scope expansion). Lets every consumer that feeds `LightGlueRuntime.match` reach for the SAME extractor (same descriptor distribution, same `descriptor_dim`) without each strategy reinventing its own preprocessing.
+- **Owned by**: AZ-343.
+- **Consumed by**: c2_5_rerank (today via `InlierCountReRanker`), c3_matcher (future concrete strategies in AZ-345 / AZ-346 / AZ-347).
+
 ### shared/helpers/wgs_converter
 
 - **Directory**: `src/gps_denied_onboard/helpers/wgs_converter.py`