[AZ-401] [AZ-400] Replay — compose_root replay-mode branch + transport seam

Wires the airborne composition root for replay-as-configuration (ADR-011):

- compose_root(config) branches on config.mode in {"live", "replay"}.
  Live behaviour is unchanged; replay builds ReplayInputAdapter,
  attaches JsonlReplaySink, and injects NoopMavlinkTransport.
- New private module runtime_root/_replay_branch.py holds the
  replay-only strategy graph + build-flag gate + calibration loader.
- Config gains Config.mode (Literal["live","replay"]) plus
  Config.replay sub-block with nested ReplayAutoSyncConfig that mirrors
  the AZ-405 AutoSyncConfig DTO; YAML loader + ENV map updated.

Absorbs the AZ-400 transport-seam retrofit that AZ-401 strictly
required but AZ-400 had not delivered:

- New MavlinkTransport Protocol (write/bytes_written/close).
- NoopMavlinkTransport (replay; build-flag gated, idempotent close,
  thread-safe byte counter).
- SerialMavlinkTransport (live, no-op restructure of existing pymavlink
  byte path; encoder retrofit to actually USE it is the AZ-558
  follow-up).

AZ-401 AC-9 (NoopMavlinkTransport.bytes_written > 0 after C8 encoders
run) is BLOCKED on AZ-558 — the encoder routing retrofit is out of
the AZ-401 task envelope (FORBIDDEN files: pymavlink_ardupilot_adapter,
msp2_inav_adapter). AZ-558 spec, batch_61_review.md, and the test's
@pytest.mark.skip rationale all carry the deferral reason.

Tests: 22 compose_root replay-branch tests + 17 transport tests.
Full regression: 2063 passed, 86 environment-skips, 1 documented
skip (AC-9 / AZ-558), 1 pre-existing flaky perf test deselected.

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

src/gps_denied_onboard/config/__init__.py

@@ -3,8 +3,10 @@
 from gps_denied_onboard.config.loader import ENV_KEY_MAP, load_config
 from gps_denied_onboard.config.schema import (
     DEFAULT_FORBIDDEN_RECORD_KINDS,
+    KNOWN_FC_DIALECTS,
     KNOWN_FC_STRATEGIES,
     KNOWN_GCS_STRATEGIES,
+    KNOWN_REPLAY_PACES,
     Config,
     ConfigError,
     FcConfig,
@@ -13,6 +15,8 @@ from gps_denied_onboard.config.schema import (
     GcsConfig,
     LogConfig,
     RecordKindPolicyConfig,
+    ReplayAutoSyncConfig,
+    ReplayConfig,
     RequiredFieldMissingError,
     RuntimeConfig,
     TileSnapshotConfig,
@@ -22,8 +26,10 @@ from gps_denied_onboard.config.schema import (
 __all__ = [
     "DEFAULT_FORBIDDEN_RECORD_KINDS",
     "ENV_KEY_MAP",
+    "KNOWN_FC_DIALECTS",
     "KNOWN_FC_STRATEGIES",
     "KNOWN_GCS_STRATEGIES",
+    "KNOWN_REPLAY_PACES",
     "Config",
     "ConfigError",
     "FcConfig",
@@ -32,6 +38,8 @@ __all__ = [
     "GcsConfig",
     "LogConfig",
     "RecordKindPolicyConfig",
+    "ReplayAutoSyncConfig",
+    "ReplayConfig",
     "RequiredFieldMissingError",
     "RuntimeConfig",
     "TileSnapshotConfig",