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.e2e.config.ts

@@ -0,0 +1,15 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    // The end-to-end tier only: the same CLI seam as the integration tier, but
+    // driven against a live disposable Gitea instance (see test/e2e). Provision
+    // and network round-trips need a longer timeout than the fast tiers.
+    include: ["test/e2e/**/*.test.ts"],
+    testTimeout: 30_000,
+    hookTimeout: 150_000,
+    // Without a live instance (GITEA_AXI_E2E_URL unset) every suite skips;
+    // that must be a pass, not a "no tests found" failure.
+    passWithNoTests: true,
+  },
+});