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.

.claude/spec/gitea-axi.md

@@ -39,7 +39,7 @@ It ships as both an installable npm CLI and a bundled Agent Skill, so any agent
 
 ### Language and Runtime
 
-TypeScript on Node 20+, matching the `gh-axi` reference implementation.
+TypeScript on the supported Node long-term-support majors — currently 22 and 24, as declared in the manifest's engine range and matrixed over by continuous integration.
 ESM module format.
 
 ### Implementation Strategy

.claude/tasks/0040-ci-node-matrix-and-new-tiers.md

@@ -24,11 +24,38 @@ The workflow keeps its container-and-npm shape and its GitHub Actions compatibil
 
 ## Acceptance criteria
 
-- [ ] The workflow runs a matrix over the two supported Node versions, and no leg runs an end-of-life Node.
-- [ ] The manifest's declared engine range names exactly the versions the matrix tests.
-- [ ] The packaging tier's engine assertion matches the narrowed range and passes.
-- [ ] The live end-to-end tier runs on the highest leg only.
-- [ ] The benchmark harness tier runs on every leg, under its own runner configuration.
-- [ ] The packaging tier runs on the highest leg only.
-- [ ] The benchmark smoke tier does not run.
-- [ ] The workflow syntax stays GitHub-Actions-compatible.
+- [x] The workflow runs a matrix over the two supported Node versions, and no leg runs an end-of-life Node.
+- [x] The manifest's declared engine range names exactly the versions the matrix tests.
+- [x] The packaging tier's engine assertion matches the narrowed range and passes.
+- [x] The live end-to-end tier runs on the highest leg only.
+- [x] The benchmark harness tier runs on every leg, under its own runner configuration.
+- [x] The packaging tier runs on the highest leg only.
+- [x] The benchmark smoke tier does not run.
+- [x] The workflow syntax stays GitHub-Actions-compatible.
+
+## Implementation Notes
+
+The supported majors are 22 and 24 — the two current long-term-support lines, and the pair that brackets the nixpkgs default the flake already builds against (24.18.0).
+The engine range became `^22 || ^24` rather than `>=22`, so it names those two majors and nothing else; a bare floor would have re-promised the odd-numbered 23, which is itself end-of-life.
+
+The single matrix job was kept rather than split into a matrixed job plus a separate single-version job for the once-only tiers.
+The acceptance criteria are phrased in terms of matrix legs, one job keeps the version list in exactly one place, and the task asked that the workflow keep its container-and-npm shape.
+The cost is that the Gitea service container starts on the Node 22 leg without the end-to-end tier consuming it — cheap next to running that tier twice, which is what the spec's rationale was actually guarding against.
+
+The once-only steps condition on `matrix.highest`, a flag attached to the `24` leg through a `strategy.matrix.include` entry, rather than on `matrix.node == '24'` at each site.
+An `include` entry whose keys match an existing combination augments that leg rather than adding a new one, on both GitHub Actions and Gitea Actions, and an undefined context property is falsy on the other leg.
+
+Two consequential changes beyond the criteria, both surfaced by review:
+
+`@types/node` moved from `^20.19.0` to `^22.20.1`.
+It was the last Node 20 reference left in the manifest, and the typecheck runs on every leg.
+It tracks the *floor* rather than the highest leg deliberately: typings for 24 would let source compile against APIs the Node 22 leg does not have.
+
+`.claude/spec/gitea-axi.md`'s "Language and Runtime" section still read "TypeScript on Node 20+", which this change falsified.
+
+Verified by running the whole matrix's worth of tiers locally through `nix develop`: typecheck, the fast tier with coverage thresholds (410 tests), the benchmark harness tier under its own runner configuration (117), and the full packaging tier (7), plus `nix build .#gitea-axi` after the lockfile moved.
+The workflow was parsed with `yq` to confirm the matrix, the container expression, and the two `if:` conditions land where intended.
+The live end-to-end tier was not run locally — it needs a disposable Gitea instance, and the diff only gates it.
+
+One follow-up worth flagging: `vitest.bench.config.ts` sets `passWithNoTests: true`, so if its include glob ever broke, the new benchmark step would go green while running nothing — precisely the failure mode this task cites as the reason to add the step.
+Pre-existing, and left alone here rather than widened into a test-configuration change.