[AZ-625] Phase E.5: airborne_bootstrap c5_isam2_graph_handle ordering

Wire the airborne bootstrap to seed pre_constructed['c5_isam2_graph_handle']
so c4_pose's compose-time lookup is satisfied (c4_pose runs before c5_state in
topological order; the iSAM2 graph handle is built INSIDE the C5 estimator's
constructor and so must be produced eagerly at bootstrap time).

build_pre_constructed now invokes a new internal _build_c5_state_estimator_pair
helper that calls state_factory.build_state_estimator once, captures the
(estimator, handle) tuple, and seeds two slots: 'c5_isam2_graph_handle' for
C4's lookup, and an internal '_c5_prebuilt_estimator' look-aside key for the
C5 wrapper's short-circuit. _c5_state_wrapper checks the look-aside key first
and returns the prebuilt instance as-is — the SAME object the handle was
extracted from, so c4_pose._isam2_handle and c5_state._isam2_handle reference
ONE object across the C4 / C5 seam (AC-625.3 cross-seam identity invariant).

C5_STATE_BUILD_FLAGS mirrors state_factory._STATE_BUILD_FLAGS so the bootstrap
can name the gating BUILD_STATE_* flag in operator errors before the lower
level StateEstimatorConfigError fires (AC-625.2). When the factory itself
rejects the configuration with the flag ON, the error wraps into
AirborneBootstrapError with __cause__ preserved (matches AZ-621 / AZ-622
patterns).

Constraints respected per AZ-618 umbrella: no per-component factory signature
changed; additive on top of AZ-619..AZ-623; no edits under state_factory,
pose_factory, or c5_state internals.

Tests: tests/unit/runtime_root/test_az625_c5_isam2_graph_handle_ordering.py
adds 8 tests covering AC-625.1..3 (presence + Protocol conformance, internal
key invariant, BUILD-flag-OFF error, unknown-strategy error, factory error
wrapping, cross-seam identity, wrapper short-circuit, wrapper fallback).
Autouse stubs added to test_az619/620/621/622/623 so prior phase tests stay
isolated from the new builder.

Quality gates: ruff format clean, ruff lint clean, 32/32 phase tests pass,
255/255 runtime_root + c5_state regression suite passes. Code review verdict
PASS (2 Low findings; full report in
_docs/03_implementation/reviews/batch_95_review.md).

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

_docs/_autodev_state.md

@@ -8,8 +8,8 @@ status: in_progress
 sub_step:
   phase: 16
   name: batch-loop
-  detail: "batch 94 done; next: batch 95 = AZ-625 (handle ordering, 3cp); AZ-624 blocked on AZ-625"
+  detail: "batch 95 done; next: batch 96 = AZ-624 (Phase F, 3cp)"
 retry_count: 0
 cycle: 1
 tracker: jira
-last_completed_batch: 94
+last_completed_batch: 95