Phase 6: enforce the quality gate in CI and export the V4.7 review log

Adds .github/workflows/quality-gate.yml, running the gate on push and pull
request. CI invokes `pre-commit run --all-files` rather than restating the
`ruff check` and `ty check` commands, so the checks keep a single definition
in .pre-commit-config.yaml and local and CI cannot drift (plan task 2).

The workflow writes a .env file rather than exporting an environment
variable. The two are not equivalent here: Settings reads the .env file,
while the external-test skip guard reads os.getenv, so an exported variable
un-skips the external tests and sends them to the network. Measured in CI:
no .env gave 115 failures and 18 errors, an exported dummy key gave 3
failures, and a written .env file reproduced the local baseline exactly.

Negative-tested on a scratch branch: a deliberate lint error failed the run
at `ruff check` with exactly the planted errors, confirming the gate blocks
rather than merely reporting (plan task 4). The subsequent clean run passed
ruff and ty and reported 295 passed, 4 skipped, matching local and
confirming the four credential-gated tests skip cleanly (plan task 3).

That first green run caught a real platform-dependent defect. PromptStore
rejected non-direct-child names via `Path(name).name != name`, which is
platform-dependent: on POSIX a backslash is an ordinary filename character,
so "nested\prompt.md" passed the guard and failed later as NOT_FOUND rather
than VALIDATION. Windows cannot reproduce it. No traversal was possible,
since the path.parent != root check still held, so the impact was a wrong
error category and a red gate. Both separators are now rejected explicitly,
matching the ^[^/\\]+$ pattern config.PromptFilename already used.

Also exports docs/ver4.7/review_log_v4_7.md, the working record kept across
all six phases: 50 entries, 1 still open. The open entry is a pre-existing
/ui redirect defect found during the Phase 3 UI walk and deliberately left
unfixed as outside the V4.7 scope boundary.

Co-authored-by: Copilot App <[email protected]>

src/transcription/services/prompts.py

@@ -104,8 +104,11 @@ class PromptStore:
 
     def _resolve_existing_prompt(self, name: str) -> Path:
         normalized_name = name.strip()
+        # Path().name is platform-dependent: POSIX treats "\" as an ordinary filename
+        # character, so reject both separators explicitly to match config.PromptFilename.
         if (
             not normalized_name
+            or any(separator in normalized_name for separator in ("/", "\\"))
             or Path(normalized_name).name != normalized_name
             or Path(normalized_name).suffix.lower() != PROMPT_EXTENSION
         ):