feat(gitea): add gitea-branches skill (branches + commits)

Adds plugins/gitea/skills/gitea-branches/ per ADR 0011, covering
list_branches/create_branch/delete_branch (migrated from the flat
plugins/bin/skills/gitea/ dispatch) plus list_commits/get_commit (new
read-only commit-history domain). Call signatures were re-verified live
via ToolSearch against the deployed gitea-mcp server rather than copied
from api-reference.md, per issue #6 comment #849's root-cause fix.

Bumps the gitea plugin to 1.1.0 in both manifests for the new skill.

plugins/gitea/plugin.json

@@ -10,10 +10,14 @@
     "issues",
     "prs",
     "milestones",
-    "releases"
+    "releases",
+    "branches"
   ],
   "license": "MIT",
   "mcpServers": ".mcp.json",
   "name": "gitea",
-  "version": "1.0.0"
+  "skills": [
+    "skills/"
+  ],
+  "version": "1.1.0"
 }