[AZ-619] Phase A: build_pre_constructed seeds c13_fdr + clock

Adds airborne_bootstrap.build_pre_constructed(config) returning a
dict with the two foundational keys: a per-binary shared FdrClient
under "c13_fdr" (via make_fdr_client with the new
AIRBORNE_MAIN_PRODUCER_ID constant) and a fresh WallClock under
"clock". Phases B..F (AZ-620..AZ-624) extend this function
additively without breaking the AZ-619 contract.

The c13_fdr instance is identity-stable across calls (per the
make_fdr_client per-producer cache) so callers can call
build_pre_constructed twice and get the same FdrClient back -
AC-619.2.

Replay-mode override is unchanged: compose_root merges
replay_components over pre_constructed so the WallClock here is
replaced by TlogDerivedClock in replay binaries (existing
contract documented in compose_root's docstring).

Tests: 5 new unit tests under tests/unit/runtime_root/
test_az619_pre_constructed_phase_a.py, all passing. AZ-591 not
regressed (12/12 in the combined run).

Spec moved to _docs/02_tasks/done/.

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

src/gps_denied_onboard/runtime_root/airborne_bootstrap.py

@@ -51,8 +51,10 @@ from __future__ import annotations
 import logging
 import os
 from collections.abc import Mapping
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, Final
 
+from gps_denied_onboard.clock.wall_clock import WallClock
+from gps_denied_onboard.fdr_client.client import make_fdr_client
 from gps_denied_onboard.runtime_root import register_strategy
 from gps_denied_onboard.runtime_root.matcher_factory import build_matcher_strategy
 from gps_denied_onboard.runtime_root.pose_factory import build_pose_estimator
@@ -66,12 +68,27 @@ if TYPE_CHECKING:
     from gps_denied_onboard.config import Config
 
 __all__ = [
+    "AIRBORNE_MAIN_PRODUCER_ID",
     "AIRBORNE_REQUIRED_PRE_CONSTRUCTED_KEYS",
     "AirborneBootstrapError",
+    "build_pre_constructed",
     "register_airborne_strategies",
 ]
 
 
+AIRBORNE_MAIN_PRODUCER_ID: Final[str] = "airborne_main"
+"""Producer ID for the per-binary shared FdrClient placed under
+``pre_constructed['c13_fdr']``.
+
+Per-component callers can still obtain their own FdrClient via
+``make_fdr_client(<their_slug>, config)`` — the cache in
+:mod:`gps_denied_onboard.fdr_client.client` ensures one instance per
+``producer_id``. The ``"airborne_main"`` instance is the one passed via
+``pre_constructed`` for the wrappers that accept ``fdr_client=`` as a
+kwarg.
+"""
+
+
 _LOG = logging.getLogger("gps_denied_onboard.runtime_root.airborne_bootstrap")
 
 
@@ -365,6 +382,30 @@ _AIRBORNE_REGISTRATIONS: tuple[
 )
 
 
+def build_pre_constructed(config: "Config") -> dict[str, Any]:
+    """Build the airborne ``pre_constructed`` dict for :func:`compose_root`.
+
+    AZ-619 (Phase A) lands the foundational keys ``c13_fdr`` and ``clock``.
+    Phases B..F (AZ-620..AZ-624) extend this function to populate the
+    remaining 10 keys in :data:`AIRBORNE_REQUIRED_PRE_CONSTRUCTED_KEYS`.
+
+    Returns a fresh dict on each call. The ``c13_fdr`` instance is cached
+    inside :func:`make_fdr_client` (per-producer cache) so two calls within
+    the same process return dicts where ``pre_constructed['c13_fdr']`` is
+    the SAME object — AC-619.2. ``clock`` is a fresh :class:`WallClock`
+    each call (stateless; the cache would be a no-op).
+
+    Replay-mode override: :func:`compose_root` merges ``replay_components``
+    over ``pre_constructed`` so the :class:`WallClock` here is replaced by
+    the replay branch's :class:`TlogDerivedClock`. That's intentional and
+    matches the contract in :func:`compose_root`'s docstring.
+    """
+    return {
+        "c13_fdr": make_fdr_client(AIRBORNE_MAIN_PRODUCER_ID, config),
+        "clock": WallClock(),
+    }
+
+
 def register_airborne_strategies() -> None:
     """Register every airborne (component, strategy) pair into ``_STRATEGY_REGISTRY``.