fix(webhook): label re-read must hit /api/v1, not the bare host

GITEA_API is the host with no version prefix — ai_review._get / _post append
/api/v1 per call. The re-read helper didn't, so it 404'd on every review and
silently fell back to the payload's verdict: "could not re-read labels for
gitea_admin/pragent#10: HTTP Error 404" in the pod log, usage block still
missing. Caught by labelling PR #10 AI-REVIEW then AI-USAGE, which is the
exact sequence the fix exists to handle.

Test asserts the composed URL, since a wrong path here fails silently by
design (the helper swallows errors so a review is never lost over a usage
section).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B11e8TZZxJyzHW7jj7KWUN

tests/pilot/test_webhook_server.py

@@ -162,6 +162,27 @@ def test_run_review_keeps_usage_off_when_label_absent(monkeypatch):
     assert seen["report_usage"] is False
 
 
+def test_fetch_current_labels_hits_the_versioned_api_path(monkeypatch):
+    # GITEA_API is the bare host; the /api/v1 prefix is the caller's job.
+    # Getting this wrong 404s silently and the opt-in is lost — which is
+    # exactly what shipped the first time.
+    seen = {}
+
+    class _Resp:
+        def read(self): return b'[{"name": "AI-USAGE"}]'
+        def __enter__(self): return self
+        def __exit__(self, *a): return False
+
+    def _urlopen(req, timeout=None):
+        seen["url"] = req.full_url
+        return _Resp()
+
+    monkeypatch.setattr(ws.urllib.request, "urlopen", _urlopen)
+    out = ws._fetch_current_labels("o/r", "9")
+    assert out == [{"name": "AI-USAGE"}]
+    assert seen["url"] == f"{ws.GITEA_API}/api/v1/repos/o/r/issues/9/labels"
+
+
 def test_label_reread_failure_is_not_fatal(monkeypatch):
     # A dead API must not take the review down with it — the re-read is a
     # best-effort upgrade of an opt-in flag, nothing more.