ci: add end-to-end tier and Gitea Actions workflow (task 0019)

Add the end-to-end test tier: a Gitea Actions workflow (GitHub-compatible)
that runs the unit+integration tiers plus e2e tests against a pinned
disposable Gitea service container. The e2e suite provisions its own repo,
token, and seed data over HTTP and drives the real CLI seam, gated on
GITEA_AXI_E2E_URL so the default suite stays dependency-free.

A fixture-vs-live shape guard anchors the issue-list FieldDef paths against
both the recorded fixture and the live response, failing on divergence.

vitest.config.ts

@@ -2,6 +2,9 @@ import { defineConfig } from "vitest/config";
 
 export default defineConfig({
   test: {
+    // Unit + integration tiers: fast, no external dependencies. The end-to-end
+    // tier under test/e2e needs a live Gitea instance and runs via `test:e2e`.
     include: ["test/**/*.test.ts"],
+    exclude: ["test/e2e/**"],
   },
 });