gitea: give the controller what it maps a pull request onto the graph with; set both check statuses; protect a branch by tool (hq ADR 0237)

The controller now decides what a pull request's check runs from the mesh's module
graph, so the announcement carries the changed directories that hold a module at the
head and whether the head has a merge-check.sh. A verdict sets mesh/merge-gate (the
gate, with the modules it judged) and mesh/repo-check (the repository's own tests).
gitea_branch_protection_get/set let the operator's agent make those statuses required.

The catalogue's merge-check.sh leaves the gate to the build seat and keeps its own layer:
every manifest through module check, and the touched Go modules' tests.

modules/gitea/tsconfig.json

@@ -8,5 +8,5 @@
     "skipLibCheck": true,
     "noEmit": true
   },
-  "include": ["client.ts", "token.ts", "index.ts", "provisioner/index.ts", "tools/index.ts"]
+  "include": ["client.ts", "token.ts", "pulls.ts", "protection.ts", "index.ts", "provisioner/index.ts", "tools/index.ts"]
 }