[AZ-342] C2.5 ReRankStrategy: Protocol + DTOs + factory + composition

Foundational scaffolding for the InlierCountReRanker (AZ-343) and
the future C3 CrossDomainMatcher consumer (AZ-344). No concrete
re-ranker is implemented here.

* ReRankStrategy Protocol (single rerank(frame, vpr_result, n,
  calibration) -> RerankResult method) with all 8 invariants in the
  docstring — notably INV-8 drop-and-continue (per-candidate failure
  NEVER propagates unless every candidate fails).
* DTOs moved to L1 _types/rerank.py — RerankCandidate, RerankResult;
  frozen+slots; tuple-not-list for RerankResult.candidates; tile_id
  encoded as (zoom_level, lat, lon) tuple to keep _types/ free of any
  c6_tile_cache (L3) import per module-layout.md.
* Error family: RerankError + RerankBackboneError +
  RerankAllCandidatesFailedError. Only RerankAllCandidatesFailedError
  escapes rerank(); RerankBackboneError is caught inside the per-
  candidate loop, logged ERROR, FDR-stamped, candidate dropped.
* C2_5RerankConfig (strategy enum default "inlier_count", top_n int
  default 3) with strict validation at load; registered into
  Config.components on c2_5_rerank import.
* build_rerank_strategy(config, *, tile_store, lightglue_runtime)
  factory: 1-strategy resolution table, lazy import,
  BUILD_RERANK_<variant> gate, ImportError → StrategyNotAvailableError
  mapping. The shared LightGlueRuntime is constructor-injected
  (R14 fix: neither C2.5 nor C3 owns its lifecycle).

Renamed the Protocol from the existing stub "RerankStrategy" to
"ReRankStrategy" to match the contract; updated module-layout.md.
Removed the legacy RerankResult shape from _types/vpr.py — the
v1.0.0 shape lives in _types/rerank.py.

Excluded per task spec:
* Concrete InlierCountReRanker (AZ-343).
* C3 matcher protocol task (AZ-344, next in batch).
* AC-9 single-thread binding + AC-10 LightGlueRuntime identity-share
  between C2.5/C3 — deferred per task spec Risk 3 until the generic
  compose_root thread-binding registry and the C3 factory both land.

Tests: AC-1..AC-8 + AC-11 + NFR-perf-factory in
tests/unit/c2_5_rerank/test_protocol_conformance.py. The legacy
smoke test is removed. Full sweep: 997 passed (one pre-existing
flake in test_az296_takeoff_abort, subprocess timing, unrelated to
this commit; passes in isolation).

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

src/gps_denied_onboard/components/c2_5_rerank/config.py

@@ -0,0 +1,54 @@
+"""C2.5 ReRankStrategy config block (AZ-342).
+
+Registered into ``config.components['c2_5_rerank']`` by the package
+``__init__.py``. The composition-root factory
+:func:`gps_denied_onboard.runtime_root.rerank_factory.build_rerank_strategy`
+reads this block to select the strategy and configure the top-N cut.
+
+``top_n`` is the strategy-side cap on the returned
+:attr:`RerankResult.candidates` length; the composition root binds
+``n`` per-frame from this value (default 3 per the epic's K=10 → N=3
+spec).
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Final
+
+from gps_denied_onboard.config.schema import ConfigError
+
+__all__ = [
+    "C2_5RerankConfig",
+    "KNOWN_STRATEGIES",
+]
+
+KNOWN_STRATEGIES: Final[frozenset[str]] = frozenset({"inlier_count"})
+
+
+@dataclass(frozen=True)
+class C2_5RerankConfig:
+    """Per-component config for C2.5 ReRank.
+
+    ``strategy`` selects exactly one of the registered re-rankers
+    (today only ``inlier_count``); the composition-root factory
+    respects compile-time ``BUILD_RERANK_<variant>`` gating on top
+    of this label.
+
+    ``top_n`` is the per-frame N cap (1..K-1). Default 3 (the epic's
+    K=10 → N=3 spec).
+    """
+
+    strategy: str = "inlier_count"
+    top_n: int = 3
+
+    def __post_init__(self) -> None:
+        if self.strategy not in KNOWN_STRATEGIES:
+            raise ConfigError(
+                f"C2_5RerankConfig.strategy={self.strategy!r} not in "
+                f"{sorted(KNOWN_STRATEGIES)}"
+            )
+        if self.top_n < 1:
+            raise ConfigError(
+                f"C2_5RerankConfig.top_n must be >= 1; got {self.top_n}"
+            )