fix: address the Copilot review of the Ace editor

- `isProgressToken` used `Number.isInteger`, but zod 4's `.int()` rejects
  anything past `MAX_SAFE_INTEGER` — verified against the pinned zod — so an
  unsafe integer passed the guard and was left for the server to reject. Now
  `isSafeInteger`, with the boundary covered in both directions.

- `echoed` held only what this component last emitted, so it went stale the
  moment an external value was applied: A → B → A stranded the editor on B,
  because the second A matched the entry left from before B arrived and was
  dismissed as our own echo. It now advances to whatever is on screen.

- `Input.Wrapper` associates a *Mantine* input through context, and Ace is not
  one — it renders its own DOM. The wrapper's label and error node therefore
  pointed at nothing: the editor was never marked `aria-invalid`, never
  described by the error text, and its visible label did not focus it. Wired
  explicitly through the wrapper's id in an effect.

- Removed two leftover `[dbg]` logs an earlier regex cleanup missed.

- Documented the editor integration and the shared `cssVariablesResolver` in
  the web README, per the rule about new dependencies and patterns. Both
  footguns are recorded: the `?url` worker import, and the gutter override
  keying off Ace's cssClass rather than the theme module name.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0177mPHAdECD18nLLCTwR5rh
Signed-off-by: cliffhall <cliff@futurescale.com>

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

@@ -1419,6 +1419,10 @@ describe("InspectorClient", () => {
       ["an array", [1]],
       ["null", null],
       ["a boolean", true],
+      // Past `Number.MAX_SAFE_INTEGER` the float64 value is no longer the
+      // integer it was written as, and zod 4's `.int()` rejects it — so
+      // `Number.isInteger` is too loose a check here.
+      ["an unsafe integer", Number.MAX_SAFE_INTEGER + 1],
     ])(
       "drops a reserved progressToken that is %s rather than sending it",
       async (_label, badToken) => {
@@ -1511,6 +1515,8 @@ describe("InspectorClient", () => {
     it.each([
       ["a string", "tok-1"],
       ["an integer", 7],
+      // The boundary itself is still valid.
+      ["the largest safe integer", Number.MAX_SAFE_INTEGER],
     ])("keeps a valid progressToken that is %s", async (_label, token) => {
       client = new InspectorClient(
         {