feat: add PR/release/branch/milestone/comment write tools

Adds six opt-in write tools (write-mode + policy + per-user permission still
enforced; no destructive or admin actions):

- create_pull_request (POST /pulls)
- create_release / edit_release (POST/PATCH /releases)
- create_branch (POST /branches; create only, no deletion)
- create_milestone (POST /milestones)
- edit_issue_comment (PATCH /issues/comments/{id})

Each: arg schema (extra=forbid, GitRef on branch/ref-like fields), Gitea client
method with url-encoded path segments, handler that surfaces auth errors, MCP
registration (write_operation=True), server wiring, docs, and success tests.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/aegis_gitea_mcp/mcp_protocol.py

@@ -426,6 +426,112 @@ AVAILABLE_TOOLS: list[MCPTool] = [
         },
         write_operation=True,
     ),
+    _tool(
+        "create_pull_request",
+        "Open a pull request from head into base (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "title": {"type": "string"},
+                "head": {"type": "string", "description": "Source branch"},
+                "base": {"type": "string", "description": "Target branch"},
+                "body": {"type": "string", "default": ""},
+            },
+            "required": ["owner", "repo", "title", "head", "base"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
+    _tool(
+        "create_release",
+        "Create a release for a tag (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "tag_name": {"type": "string"},
+                "name": {"type": "string", "default": ""},
+                "body": {"type": "string", "default": ""},
+                "draft": {"type": "boolean", "default": False},
+                "prerelease": {"type": "boolean", "default": False},
+                "target": {"type": "string", "description": "Target commitish/branch"},
+            },
+            "required": ["owner", "repo", "tag_name"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
+    _tool(
+        "edit_release",
+        "Edit an existing release (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "release_id": {"type": "integer", "minimum": 1},
+                "name": {"type": "string"},
+                "body": {"type": "string"},
+                "draft": {"type": "boolean"},
+                "prerelease": {"type": "boolean"},
+            },
+            "required": ["owner", "repo", "release_id"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
+    _tool(
+        "create_branch",
+        "Create a branch, optionally from an existing branch (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "new_branch_name": {"type": "string"},
+                "old_branch_name": {"type": "string", "description": "Source branch (optional)"},
+            },
+            "required": ["owner", "repo", "new_branch_name"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
+    _tool(
+        "create_milestone",
+        "Create a repository milestone (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "title": {"type": "string"},
+                "description": {"type": "string", "default": ""},
+                "due_on": {"type": "string", "description": "ISO8601 due date (optional)"},
+            },
+            "required": ["owner", "repo", "title"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
+    _tool(
+        "edit_issue_comment",
+        "Edit an existing issue or PR comment (write-mode only).",
+        {
+            "type": "object",
+            "properties": {
+                "owner": {"type": "string"},
+                "repo": {"type": "string"},
+                "comment_id": {"type": "integer", "minimum": 1},
+                "body": {"type": "string"},
+            },
+            "required": ["owner", "repo", "comment_id", "body"],
+            "additionalProperties": False,
+        },
+        write_operation=True,
+    ),
 ]