chore(scripts): rename the local pre-push gate off ci, and guard it out of CI (#2146)

The root `ci` script was never what runs in GitHub CI, and the name worked
against us three ways: it collides with the built-in `npm ci` (which does
something else entirely and is one keystroke away), it invites the
cross-engine passes into a workflow by looking like the thing a workflow
should call, and it blurs "GitHub CI" and "the local gate" in every doc
that names it.

- Rename `ci` → `local:gate` and `ci:storybook` → `local:storybook`, with
  no back-compat alias: `npm run ci` now fails with npm's missing-script
  error, which prints the available scripts.

- Add `scripts/lib/workflow-gate.mjs` + its `test:scripts` suite, which
  runs over the repo's real `.github/workflows/**` and fails on an
  invocation of a `local:*` script, of a non-Chromium engine pass (derived
  from SUPPORTED_BROWSERS), or of `smoke:web:engine`, or on `SMOKE_BROWSER`
  set to anything but a literal `chromium`. It does not forbid
  `npm run smoke`, `smoke:web:chromium` or `smoke:tui` — those belong in CI
  and are there today. Comments are not scanned, so the workflow can still
  explain itself. This is the durable half; the rest is prose.

- Document the two-tier model once, in the root README ("Two tiers: GitHub
  CI and the local gate"), and point the other docs at it rather than
  restating the split.

- Sweep the ~40 stale references across README, AGENTS.md,
  .github/copilot-instructions.md, the client READMEs, the roadmap doc and
  the script headers. AGENTS.md and copilot-instructions.md change
  together, per the mirror rule.

No gate changes what it actually runs.

Signed-off-by: Cliff Hall <cliff@futurescale.com>
Signed-off-by: cliffhall <cliff@futurescale.com>

clients/web/src/components/elements/AppRenderer/AppRenderer.test.tsx

@@ -552,7 +552,7 @@ describe("AppRenderer", () => {
       // pending here. Observed failing exactly once that way, with 0 calls.
       //
       // The default 1000ms then turned out not to be enough either — it failed
-      // twice in a row in `npm run ci` (at ~1021ms, still 0 calls) while
+      // twice in a row in `npm run local:gate` (at ~1021ms, still 0 calls) while
       // passing every time this file runs alone, which is the signature of a
       // budget that is too tight rather than of a broken observer. Raised
       // rather than retried: a `waitFor` that is generous costs nothing on the

clients/web/src/test/integration/mcp/inspectorClient.test.ts

@@ -108,7 +108,7 @@ async function getTool(client: InspectorClient, name: string): Promise<Tool> {
  * legitimate thing to exercise, but `disconnect()` closes the SDK client, which
  * rejects every pending request with "Connection closed" — and a floating
  * promise makes that an *unhandled* rejection, which vitest counts as a run
- * error and fails `npm run ci` even though every test passes (#1947).
+ * error and fails `npm run local:gate` even though every test passes (#1947).
  *
  * Attach the handler at call time (not after the assertions) so there is no
  * window in which the rejection can escape, then finish through