pilot: central webhook service (user-level Gitea webhook + AI-REVIEW gate)

- pilot/webhook_server.py: stdlib HTTP receiver. HMAC-verifies X-Gitea-Signature,
  gates on pull_request action + AI-REVIEW label, runs review_pr in a background
  thread (responds 202 immediately so Gitea's delivery timeout never fires).
  Accepts both GitHub-style (labeled/synchronize) and Gitea event-type-style
  (label_updated/synchronized) action names.
- pilot/ai_review.py: extract review_pr() core so both the CI run() and the
  webhook server share one review path. run() is now an env-driven wrapper.
- pilot/README-webhook.md: architecture, onboarding, one-time per-owner
  user-webhook setup, the Gitea 1.26.1 system-webhook bug, the SSRF
  ALLOWED_HOST_LIST change, K8s deploy + script-update recipe.
- README.md + design doc: note the webhook service as the preferred delivery
  path (partially reverses 'central webhook = non-goal', pilot only).

Gitea 1.26.1 system webhooks broken (POST /admin/hooks -> 201 but never
persists); user-level webhooks (one per repo-owner) are the working fallback.
Gitea SSRF allow-list blocks in-cluster webhook targets by default; required a
scoped [webhook] ALLOWED_HOST_LIST addition + gitea restart.

E2E verified 2026-08-17: pragent-bot reviewed gitea_admin/pragent PR #2 and
masi/portfolio PR #3 via the webhook service (glm-5.2:cloud).

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

pilot/ai_review.py

@@ -187,33 +187,57 @@ def _need(name: str) -> str:
     return v
 
 
-def run() -> int:
-    api = _need("GITEA_API")
-    repo = _need("GITEA_REPOSITORY")
-    index = _need("PR_INDEX")
-    token = _need("PRAGENT_BOT_TOKEN")
-    ollama_url = _need("OLLAMA_URL")
-    model = _need("OLLAMA_MODEL")
-    title = os.environ.get("PR_TITLE", "")
-    body = os.environ.get("PR_BODY", "")
-    sha = os.environ.get("PRAGENT_SHA", "")
-    max_tokens = int(os.environ.get("OLLAMA_MAX_TOKENS", "6000"))
-    max_chars = int(os.environ.get("DIFF_MAX_CHARS", "150000"))
+def review_pr(
+    api: str,
+    repo: str,
+    index: str,
+    title: str,
+    body: str,
+    sha: str,
+    token: str,
+    ollama_url: str,
+    model: str,
+    max_tokens: int = 6000,
+    max_chars: int = 150000,
+) -> bool:
+    """Run one review and post it as a PR comment.
 
+    Returns True on success, False on failure (failure note is posted when
+    possible). Never raises — fail-open by design. Both the CI `run()` entry
+    point and the central webhook server call this.
+    """
     try:
-        diff, truncated, _orig = fetch_pr_diff(api, repo, index, token, max_chars)
+        diff, _truncated, _orig = fetch_pr_diff(api, repo, index, token, max_chars)
         if not diff.strip():
             post_review(api, repo, index, token, format_review_body("No diff content to review.", model, sha))
-            return 0
+            return True
         user_prompt = build_user_prompt(title, body, diff)
         findings = call_model(ollama_url, model, SYSTEM_PROMPT, user_prompt, max_tokens)
         post_review(api, repo, index, token, format_review_body(findings, model, sha))
+        return True
     except Exception as e:  # fail-open
         try:
             post_review(api, repo, index, token, format_review_body(f"⚠️ AI review failed: {e}", model, sha))
         except Exception as e2:
             print(f"pragent: could not post failure note: {e2}", file=sys.stderr)
         print(f"pragent: review failed: {e}", file=sys.stderr)
+        return False
+
+
+def run() -> int:
+    review_pr(
+        api=_need("GITEA_API"),
+        repo=_need("GITEA_REPOSITORY"),
+        index=_need("PR_INDEX"),
+        title=os.environ.get("PR_TITLE", ""),
+        body=os.environ.get("PR_BODY", ""),
+        sha=os.environ.get("PRAGENT_SHA", ""),
+        token=_need("PRAGENT_BOT_TOKEN"),
+        ollama_url=_need("OLLAMA_URL"),
+        model=_need("OLLAMA_MODEL"),
+        max_tokens=int(os.environ.get("OLLAMA_MAX_TOKENS", "6000")),
+        max_chars=int(os.environ.get("DIFF_MAX_CHARS", "150000")),
+    )
     return 0