feat(forge): adapter seam + Gitea implementation — optional read access to the operator's forge (#2689)

Step 4 of milestone 288 (decision #2686). services/forge.py defines the
contract steps 5-7 consume — read_file (content + last_commit_sha, the
provenance stamp), default_branch, resolve_repo, check — with GiteaForge
as the first implementation over the REST contents/repo/version/user
endpoints. Repo identity reuses normalize_repo_key: the host segment
selects whether this forge serves a recorded repo, the remainder is the
API path, so no new identity scheme exists. Read-only by construction;
errors never carry the token; first outbound-HTTP timeout convention
(5s total, no retries — the consumer's fallback is the retry policy).

OPTIONAL per instance (rule #115): get_forge() returns None when
unconfigured and every consumer treats None as today's behavior. Config
lives in admin settings (Settings → Config → Git Forge: kind/base
URL/token, save + test-connection probe reporting version + identity),
with FORGE_* env / Docker-secret fallbacks; DB wins so a UI edit can't
silently lose to an env var. Token treatment follows the smtp_password
convention (masked on read, mask-sentinel skipped on write, absent from
audit details) — and wiring it surfaced that the generic GET/PUT
/api/settings dump bypassed that masking for the owning admin's raw KV
rows, so secret keys are now masked there too (fixes the same exposure
for smtp_password).

Contract tests run against httpx.MockTransport as the fake forge — the
reference behaviors the GitHub adapter (step 8) must reproduce — plus
the off-by-default gate, partial-config-is-off, env-vs-DB precedence,
and route/mask structural checks. Also: the step-2 definition detector
learned to skip dunders after flagging __init__ as 'already defined in
4 files' on this step's own build — guaranteed noise for a hint that
must stay trustworthy.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/routes/settings.py

@@ -16,13 +16,27 @@ logger = logging.getLogger(__name__)
 
 settings_bp = Blueprint("settings", __name__, url_prefix="/api/settings")
 
+# Keys whose values are credentials. The admin endpoints that own them mask on
+# read and skip the mask on write; this generic KV surface has to apply the
+# same treatment, or it silently un-masks what those endpoints masked — the
+# rows live on the admin's own user_id, so the plain GET returned them raw.
+_SECRET_KEYS = frozenset({"smtp_password", "forge_token"})
+_SECRET_MASK = "********"
+
+
+def _masked(settings: dict) -> dict:
+    return {
+        k: (_SECRET_MASK if k in _SECRET_KEYS and v else v)
+        for k, v in settings.items()
+    }
+
 
 @settings_bp.route("", methods=["GET"])
 @login_required
 async def get_settings_route():
     uid = get_current_user_id()
     settings = await get_all_settings(uid)
-    return jsonify(settings)
+    return jsonify(_masked(settings))
 
 
 @settings_bp.route("", methods=["PUT"])
@@ -36,6 +50,10 @@ async def update_settings_route():
     to_save = {}
     for k, v in data.items():
         str_v = str(v)
+        # A masked secret round-tripping through a client is "unchanged", not
+        # a request to store the mask over the real credential.
+        if k in _SECRET_KEYS and str_v == _SECRET_MASK:
+            continue
         if not str_v:
             await delete_setting(uid, k)
         else:
@@ -45,7 +63,7 @@ async def update_settings_route():
         await set_settings_batch(uid, to_save)
 
     settings = await get_all_settings(uid)
-    return jsonify(settings)
+    return jsonify(_masked(settings))
 
 
 @settings_bp.route("/search", methods=["GET"])