fix(review): harden relay_overrides parser + polish (PR #178 review)

Addresses verified findings from the /review-pr pass on PR #178.

H1 — relay_overrides values are now type-checked
- Allowlist of recognised knobs (`video_strength`, `video_window_scale`,
  `audio_strength`, `audio_window_scale`, `audio_epsilon`) with explicit
  float-coercion. Numeric strings ("10") coerce silently; non-numeric
  values (e.g. "ten") now raise a ValueError naming the offending knob
  and showing a minimal correct example — instead of a TypeError deep
  inside `build_segments` arithmetic, or a SUCCESS render at upstream
  defaults that polluted the A/B iteration log.

H2 — malformed JSON no longer silently falls back to defaults
- `json.JSONDecodeError`, non-dict JSON (arrays, strings, bare numbers,
  null), and non-numeric values for recognised knobs all now raise
  `ValueError` with operator-actionable messages. The only silent
  fallback is the explicit empty/whitespace case — "use upstream
  defaults" is the operator's intent there.
- Typo'd keys (e.g. `viedo_strength`) log a warning naming the unknown
  keys + the recognised set, then drop the typo. Previously they were
  silently retained in the cleaned dict but never queried by
  `build_segments`, indistinguishable from a default render.

Architectural side-effect — shrinks the diff vs vendored upstream
- `_parse_relay_overrides` extracted into a stdlib-only sibling module
  `_relay_overrides.py`. `ltx_director.py` shrinks closer to upstream
  baseline (one import + one alias instead of a 30-line function body)
  and is easier to diff against `e81223a`. The parser is also now
  unit-testable without ComfyUI's `comfy_api` runtime.

L5 — tests added (31 cases, all passing)
- New `tests/forks/__init__.py` + `tests/forks/test_whatdreamscost_v1_3_2_relay_overrides.py`.
- Covers every confirmed failure mode (H1 + H2), the happy path, the
  comment-key convention, the unknown-key warning, and an allowlist-
  consistency assertion that fails loudly if `build_segments` ever
  grows a knob without the parser being updated.
- Test module uses `importlib.util.spec_from_file_location` so it can
  load the parser without walking through the package hierarchy (which
  would trigger the `comfy_api` import inside `ltx_director.py`).

L3 — `_build_line` promoted to public `build_line`
- `scripts/sync_to_dev.py` renames the private helper. The underscore
  alias is kept for one release cycle as a deprecation slot.
- `scripts/sync_to_dev_audio.py` switches to `_dev.build_line()`. No
  behaviour change; chat-report shape is bit-identical to before.

L2 — `source_ref` clarified in pin metadata
- `forks/whatdreamscost_koolook/versions/v1_3_2/UPSTREAM_PIN.yaml` and
  `forks/forks_manifest.yaml` both now spell out that `e81223a` is the
  post-v1.3.2 README-only commit on upstream's `main`, not the v1.3.2
  release tag itself. Code is byte-identical to the tagged release; the
  pin differs only in trailing docs.

L1, L4 are explicitly left alone (L1 is dead upstream cruft, kept for
minimum-diff; L4 is helper duplication tracked for a separate follow-up
issue when a third fork lands).

Verification
- ruff check . → clean
- pytest → 204 passed (173 prior + 31 new parser tests)
- tools/preflight_release.py --skip manager-meta → all PASS (static AST
  extraction still picks up LTXDirector from the fork)
- scripts/sync_to_dev_audio.py --dry-run → two-line chat report still
  emits via the renamed `build_line` helper

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/sync_to_dev.py

@@ -110,7 +110,7 @@ def _get_worktree_name() -> str:
     return REPO_ROOT.name
 
 
-def _build_line() -> str:
+def build_line() -> str:
     """Composes the two-piece header line consumed by the chat-report
     convention defined in project CLAUDE.md:
 
@@ -118,11 +118,22 @@ def _build_line() -> str:
 
     SHA falls back to ``unknown`` if git is unreachable (we always need
     SOMETHING in slot 1 — the line shape is part of the convention).
-    Worktree name comes from ``REPO_ROOT.name`` and is always present."""
+    Worktree name comes from ``REPO_ROOT.name`` and is always present.
+
+    Public — consumed by scoped per-module wrappers like
+    ``sync_to_dev_audio.py`` so every dev-sync variant emits the same
+    chat-report header.
+    """
     sha = _get_short_sha() or "unknown"
     return f"{sha} - {_get_worktree_name()}"
 
 
+# Backwards-compatible alias (the function was private until the audio
+# wrapper landed). Drop after the next release cycle once we're sure no
+# downstream caller imports the underscore name.
+_build_line = build_line
+
+
 def trigger_restart(url: str, timeout: float = 2.0) -> tuple[bool, str]:
     """Best-effort POST/GET to ComfyUI-Manager's reboot endpoint.
 
@@ -431,7 +442,7 @@ def main() -> int:
     # chat-report convention that consumes this output. Header first so
     # the maintainer's eye lands on the build identifier before the
     # mechanical sync details.
-    print(_build_line())
+    print(build_line())
     print(f"{verb} {n} entries -> {target}")
     if not args.dry_run:
         write_build_info(target, args.scope)