ci: matrix over Node 22 and 24, add the bench and packaging tiers (task 0040)

The workflow pinned Node 20, which reached end-of-life in April 2026, while
the manifest promised support down to it — so the entire claimed range below
the single tested version went unverified and its floor was unsupported.

Matrix over the two supported long-term-support majors and narrow the engine
range to `^22 || ^24`, naming exactly what is tested. Narrowing is free now
because nothing has been published and no tags exist.

The benchmark harness tier joins every leg: it is deterministic and needs no
network, and its non-default runner configuration made it easy to believe it
was running when it was not. The end-to-end and packaging tiers run on the
highest leg only, conditioned on a flag attached to that leg through a matrix
`include` entry rather than on a version number restated at each site. The
benchmark smoke tier stays out, since it would pass by skipping.

`@types/node` follows the new floor; it was the last Node 20 reference in the
manifest, and the typecheck runs on every leg.

.gitea/workflows/ci.yml

@@ -16,7 +16,22 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
-    container: node:20-bookworm
+    container: node:${{ matrix.node }}-bookworm
+
+    strategy:
+      # Every leg's result is wanted: a failure on one Node major says nothing
+      # about the other, and cancelling the sibling would hide half the answer.
+      fail-fast: false
+      matrix:
+        # The supported Node majors, matching the manifest's declared engine
+        # range. Node 20 is end-of-life and deliberately absent.
+        node: ["22", "24"]
+        # Augments the highest leg with a flag, so the steps that run once
+        # share one named condition rather than each restating a version
+        # number. Keep this entry's `node` matching the last element above.
+        include:
+          - node: "24"
+            highest: true
 
     services:
       gitea:
@@ -50,5 +65,20 @@ jobs:
       - name: Unit and integration tiers (with coverage thresholds)
         run: npm run test:coverage
 
+      # Deterministic, and needs neither network nor the agent SDK, so it runs
+      # everywhere. Its non-default runner configuration makes it an easy tier
+      # to believe is running when it is not.
+      - name: Benchmark harness tier
+        run: npm run test:bench
+
+      # Exercises the Gitea API contract rather than Node-version behaviour, so
+      # one leg is enough.
       - name: End-to-end tier
+        if: matrix.highest
         run: npm run test:e2e
+
+      # Slow, and near enough version-independent — but the only automated guard
+      # on the distribution artifact, since publishing is a manual command.
+      - name: Packaging tier
+        if: matrix.highest
+        run: npm run test:pack