Test/1396 harden managed state connect tests (#1508)

* test(state): wait for connect refresh before asserting list RPC gate (#1396)

Replace fixed double-microtask flushes in Managed*State connect-path tests with *Change event waits so the capability gate is asserted after refresh completes.

* test(state): fail fast with a readable message if a connect refresh never dispatches its change event (#1396)

The hardened connect-path gate tests now depend on the gated (capability-less /
empty-list) refresh still emitting its *Change event. A future optimization that
skipped that redundant dispatch would make these awaits hang to the vitest
per-test timeout with no clue why.

Extract the per-file waitFor*Change helpers into a shared, generically-typed
waitForChangeEvent() that races the listener against a short timeout and rejects
naming the event that never fired — turning a future hang into a fast, readable
failure. This also removes the duplicated listener/Promise boilerplate across
the five state test files. No production code changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(state): cover void-detail event resolution in waitForChangeEvent

Add a case asserting the helper still resolves for a signal-only (void-detail)
event — CustomEvent normalizes an absent detail to null, so the listener fires
and resolves rather than hanging. Closes the coverage gap noted in review.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* docs(core): correct TypedEventGeneric void-detail comment to null

CustomEvent normalizes an absent detail to null, so listeners receive null
(not undefined) for void events — as the new waitForChangeEvent void case
establishes. Comment-only; no behavior change.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: cliffhall <cliff@futurescale.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/mcp/typedEventTarget.ts

@@ -6,7 +6,8 @@
 
 /**
  * Typed event class that extends CustomEvent with type-safe detail.
- * For void events, detail is undefined.
+ * For void events the detail is omitted; CustomEvent normalizes that to `null`,
+ * so listeners receive `null` (not `undefined`) for such events.
  */
 export class TypedEventGeneric<
   EventMap extends object,