[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>

tests/unit/runtime_root/test_az619_pre_constructed_phase_a.py

@@ -0,0 +1,109 @@
+"""AZ-619 — Phase A of AZ-618: ``build_pre_constructed`` seeds c13_fdr + clock.
+
+Verifies the contract at
+``_docs/02_tasks/todo/AZ-619_pre_constructed_phase_a_c13_fdr_clock.md``:
+
+* AC-619.1: ``build_pre_constructed(default_config)`` returns a dict
+  containing keys ``c13_fdr`` (FdrClient instance) and ``clock``
+  (WallClock instance).
+* AC-619.2: invoking twice in the same process returns dicts where
+  ``c13_fdr`` is the SAME FdrClient instance (per ``make_fdr_client``
+  cache); ``clock`` may be a fresh WallClock each call.
+
+AC-619.3 (this file exists with the above tests) is satisfied by the
+existence of this module.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Iterator
+
+import pytest
+
+from gps_denied_onboard.clock.wall_clock import WallClock
+from gps_denied_onboard.config import Config
+from gps_denied_onboard.fdr_client import client as fdr_client_module
+from gps_denied_onboard.fdr_client.client import FdrClient
+from gps_denied_onboard.runtime_root.airborne_bootstrap import (
+    AIRBORNE_MAIN_PRODUCER_ID,
+    build_pre_constructed,
+)
+
+
+@pytest.fixture(autouse=True)
+def _isolated_fdr_cache() -> Iterator[None]:
+    # Arrange: every test starts with an empty FdrClient cache so AC-619.2's
+    # "same instance across calls" assertion is exercised against fresh state
+    # rather than stale cache from a prior test.
+    fdr_client_module._reset_for_tests()
+    yield
+    fdr_client_module._reset_for_tests()
+
+
+def test_ac_619_1_default_config_seeds_c13_fdr_and_clock() -> None:
+    # Arrange
+    config = Config()
+
+    # Act
+    pre_constructed = build_pre_constructed(config)
+
+    # Assert
+    assert "c13_fdr" in pre_constructed
+    assert "clock" in pre_constructed
+    assert isinstance(pre_constructed["c13_fdr"], FdrClient)
+    assert isinstance(pre_constructed["clock"], WallClock)
+
+
+def test_ac_619_1_c13_fdr_uses_airborne_main_producer_id() -> None:
+    # Arrange
+    config = Config()
+
+    # Act
+    pre_constructed = build_pre_constructed(config)
+
+    # Assert: the FdrClient is keyed under the documented producer ID so
+    # any per-component caller using the same ID gets the same instance.
+    assert pre_constructed["c13_fdr"].producer_id == AIRBORNE_MAIN_PRODUCER_ID
+
+
+def test_ac_619_2_c13_fdr_cached_across_calls() -> None:
+    # Arrange
+    config = Config()
+
+    # Act
+    first = build_pre_constructed(config)
+    second = build_pre_constructed(config)
+
+    # Assert: same FdrClient instance via make_fdr_client cache.
+    assert first["c13_fdr"] is second["c13_fdr"]
+
+
+def test_ac_619_2_clock_is_independent_instance_per_call() -> None:
+    # Arrange
+    config = Config()
+
+    # Act
+    first = build_pre_constructed(config)
+    second = build_pre_constructed(config)
+
+    # Assert: WallClock is stateless; identity-share is not contractual.
+    # Both must be valid WallClock instances. Identity may or may not match.
+    assert isinstance(first["clock"], WallClock)
+    assert isinstance(second["clock"], WallClock)
+
+
+def test_phase_a_only_seeds_two_keys() -> None:
+    """Phase A scope discipline: exactly the two documented keys.
+
+    Phases B..F (AZ-620..AZ-624) will add more keys; this test will be
+    relaxed at that point. For now it pins the AZ-619 contract precisely so
+    a regression that adds keys here without updating the spec is caught.
+    """
+    # Arrange
+    config = Config()
+
+    # Act
+    pre_constructed = build_pre_constructed(config)
+
+    # Assert
+    assert set(pre_constructed.keys()) == {"c13_fdr", "clock"}