feat: add output truncation and offset paging to all large-output tools

- coding_tools: list_files (max_entries=200, sorted), run_command
  (max_chars=8000, output_offset), grep_search (max_lines=100, offset);
  added _truncate_output helper for run_command paging
- pr_tools: get_pull_request_diff / get_pull_request_patch now truncate
  at 15k chars with hunk-boundary awareness and char_offset paging;
  get_pull_request_comments gains limit/offset paging
- issue_tools: get_issue_comments gains limit/offset paging
- file_tools: get_file_content / get_file_content_with_ref now paginate
  by line (offset=1, limit=250), matching existing read_file convention;
  added _paginate_lines helper
- research_tools: fetch_url gains char_offset parameter; _smart_truncate
  now slices from an offset and embeds next char_offset in the footer
- gitea_tools facade: all new params threaded through

gitea/tools/pr_tools.py

@@ -5,6 +5,30 @@ from typing import Any
 from gitea.client import GiteaClient
 from gitea.models import PullRequestModel, CommentModel
 
+_MAX_DIFF_CHARS: int = 15_000
+
+
+def _truncate_diff(
+    text: str,
+    max_chars: int = _MAX_DIFF_CHARS,
+    char_offset: int = 0,
+) -> str:
+    """Slice [char_offset : char_offset+max_chars] from text, cutting at a hunk boundary."""
+    total: int = len(text)
+    chunk: str = text[char_offset : char_offset + max_chars]
+    if char_offset > 0 or (char_offset + max_chars) < total:
+        # Try to cut at a diff hunk boundary (@@) for coherence
+        hunk_boundary: int = chunk.rfind("\n@@")
+        if hunk_boundary > int(len(chunk) * 0.6):
+            chunk = chunk[:hunk_boundary]
+        next_offset: int = char_offset + len(chunk)
+        chunk += (
+            f"\n\n[Diff truncated — {total} chars total. "
+            f"Showing chars {char_offset}–{next_offset}. "
+            f"Re-call with char_offset={next_offset} to read more.]"
+        )
+    return chunk
+
 
 class PRTools:
     """Tools for Gitea pull request operations."""
@@ -26,10 +50,34 @@ class PRTools:
         except Exception as e:
             return f"Error closing pull request: {str(e)}"
 
-    def get_pull_request_comments(self, owner: str, repo: str, pull_number: int) -> str:
+    def get_pull_request_comments(
+        self,
+        owner: str,
+        repo: str,
+        pull_number: int,
+        limit: int = 20,
+        offset: int = 0,
+    ) -> str:
+        """Get comments on a pull request with optional paging.
+
+        Args:
+            limit: Maximum number of comments to return (default 20).
+            offset: Zero-based comment index to start from (default 0).
+        """
         try:
-            comments: list[CommentModel] = self._client.get_pull_request_comments(owner, repo, pull_number)
-            return json.dumps([c.model_dump() for c in comments], indent=2)
+            comments: list[CommentModel] = self._client.get_pull_request_comments(
+                owner, repo, pull_number
+            )
+            total: int = len(comments)
+            page: list[CommentModel] = comments[offset : offset + limit]
+            result: str = json.dumps([c.model_dump() for c in page], indent=2)
+            if total > offset + limit:
+                next_offset: int = offset + limit
+                result += (
+                    f"\n\n[{total} comments total — showing {offset}–{offset + len(page)}. "
+                    f"Re-call with offset={next_offset} to see more.]"
+                )
+            return result
         except Exception as e:
             return f"Error getting PR comments: {str(e)}"
 
@@ -72,15 +120,45 @@ class PRTools:
         except Exception as e:
             return f"Error adding label to PR #{pr_number}: {e}"
 
-    def get_pull_request_diff(self, owner: str, repo: str, pull_number: int) -> str:
+    def get_pull_request_diff(
+        self,
+        owner: str,
+        repo: str,
+        pull_number: int,
+        max_chars: int = _MAX_DIFF_CHARS,
+        char_offset: int = 0,
+    ) -> str:
+        """Get the diff of a pull request, with truncation and offset paging.
+
+        Args:
+            max_chars: Maximum characters to return (default 15 000).
+            char_offset: Character offset to start reading from (default 0).
+                         Increment by max_chars to page through a large diff.
+        """
         try:
-            return self._client.get_pull_request_diff(owner, repo, pull_number)
+            diff: str = self._client.get_pull_request_diff(owner, repo, pull_number)
+            return _truncate_diff(diff, max_chars, char_offset)
         except Exception as e:
             return f"Error getting PR diff: {str(e)}"
 
-    def get_pull_request_patch(self, owner: str, repo: str, pull_number: int) -> str:
+    def get_pull_request_patch(
+        self,
+        owner: str,
+        repo: str,
+        pull_number: int,
+        max_chars: int = _MAX_DIFF_CHARS,
+        char_offset: int = 0,
+    ) -> str:
+        """Get the patch of a pull request, with truncation and offset paging.
+
+        Args:
+            max_chars: Maximum characters to return (default 15 000).
+            char_offset: Character offset to start reading from (default 0).
+                         Increment by max_chars to page through a large patch.
+        """
         try:
-            return self._client.get_pull_request_patch(owner, repo, pull_number)
+            patch: str = self._client.get_pull_request_patch(owner, repo, pull_number)
+            return _truncate_diff(patch, max_chars, char_offset)
         except Exception as e:
             return f"Error getting PR patch: {str(e)}"