ci: shard both suites by measured duration and split the unit suite

Vitest's --shard cut the file list into slices of equal length, which gave
the integration shards 954 s to 1 449 s. A sequencer now deals files out by
their measured duration, plus a fixed per-file cost for import and setup,
longest first to the shard with the least work, and starts the longest files
first inside a shard. Timings live in tests/durations/*.json and are
regenerated from Vitest JSON reports with scripts/test-durations.mjs; every
CI shard uploads its report.

Integration shards run three workers each, one cloned database per worker.
The unit suite runs as three projects decided per file from its source:
guards and unit share a module graph inside a worker, isolated keeps a fresh
one for every file that mocks, spies, stubs or resets. In CI it is three
duration-balanced shards next to a job for lint, format, types and the
OpenAPI drift check.

The required check names stay as they were. "Lint, Typecheck & Test" is now
the job that answers for the static checks and every unit shard, the way
"integration" already answers for its shards. The browser-install guard
recognises a direct, flags-only vitest run as a run of the unit suite.

src/__tests__/unit-suite-browser-install-guard.test.ts

@@ -23,8 +23,14 @@ import { join } from "node:path";
 
 const WORKFLOWS = join(process.cwd(), ".github", "workflows");
 
-/** `run: pnpm test` — the whole unit suite, geometry check included. */
-const RUNS_UNIT_SUITE = /^\s*(?:-\s*)?run:\s*pnpm test\s*$/m;
+/**
+ * `run: pnpm test`, or a direct `vitest run` of the unit config with flags
+ * only (the sharded CI job, the nightly shuffled run): the whole unit suite
+ * or a slice of it, geometry check included. A run that names a path or
+ * another `--config` is a different, narrower suite and does not count.
+ */
+const RUNS_UNIT_SUITE =
+  /^\s*(?:-\s*)?run:\s*pnpm test\s*$|pnpm exec vitest run(?![^\n]*--config)(?=\s*$|\s+--)/m;
 const INSTALLS_BROWSER = /playwright install --only-shell chromium/;
 
 describe("the browser the unit suite measures with", () => {