feat(robomp): added repo-scoped issue search to issue triage flow

- Added `search_issues` support to the GitHub backend and client, including `state_reason` and `is_pull_request` in issue summaries.
- Added the `gh_search_issues` host tool with repo-prefixed query handling, non-empty/restricted `repo:` validation, default and bounded `limit` values, and inbound issue filtering.
- Added proxy integration for issue search with a new `/gh/v1/search_issues` endpoint and matching proxy-client method/response parsing.
- Updated triage prompts to perform pre-`classify_issue` duplicate and already-fixed checks via search, and added tests for search query formatting, validation, and state-aware match rendering.

python/robomp/src/proxy_client.py

@@ -204,6 +204,14 @@ class GitHubProxyClient:
         )
         return [_issue_summary_from(item) for item in (data.get("items") if isinstance(data, dict) else None) or []]
 
+    async def search_issues(self, repo: str, query: str, *, limit: int = 10) -> list[IssueSummary]:
+        data = await self._request(
+            "GET",
+            "/gh/v1/search_issues",
+            params={"repo": repo, "q": query, "limit": limit},
+        )
+        return [_issue_summary_from(item) for item in (data.get("items") if isinstance(data, dict) else None) or []]
+
     async def list_comments(self, repo: str, number: int) -> list[CommentInfo]:
         data = await self._request("GET", "/gh/v1/comments", params={"repo": repo, "number": number})
         return [_comment_from(item) for item in (data.get("items") if isinstance(data, dict) else None) or []]
@@ -498,6 +506,8 @@ def _issue_summary_from(data: Any) -> IssueSummary:
         updated_at=str(data.get("updated_at") or ""),
         created_at=str(data.get("created_at") or ""),
         html_url=str(data.get("html_url") or ""),
+        state_reason=str(data.get("state_reason") or ""),
+        is_pull_request=bool(data.get("is_pull_request")),
     )