Refactor / justify codebase-wide 'as unknown as' casts (#1690) (#1756)

* core: refactor serverList.ts object↔Record casts into typed helper (#1690)

Remove the four pre-existing `as unknown as Record<string, unknown>` /
`as unknown as MCPServerConfig` casts in core/mcp/serverList.ts:

- stripInspectorFields: rewrite as clone + `delete` over INSPECTOR_FIELD_KEYS.
  Every Inspector-extension key is optional on StoredMCPServer, so the result
  is still (a subtype of) MCPServerConfig with no cast.
- oauth-strip in extractSecretsFromStored: `oauth` is optional, so a plain
  `delete stripped.oauth` is legal — drop the cast.
- mcpConfigToServerEntries: route the one genuinely-needed widening through a
  single documented `toRecord(value: object)` helper. Taking `object` makes the
  single `as Record<string, unknown>` legal (no TS2352), so the double cast
  disappears from the call site.

Net: zero `as unknown as` in serverList.ts; the one remaining structural cast
lives inside the audited toRecord helper. Behavior-neutral — existing coverage
(79 serverList tests) unchanged; full `npm run ci` passes.

Closes #1690

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* core+web+test-servers: eliminate/justify remaining `as unknown as` casts (#1690)

Codebase-wide follow-on to the serverList refactor: audit every `as unknown
as` double cast outside tests and either remove it or ensure it carries a
justifying comment (the review bar is "no *unjustified* double cast").

Removed (widened via a shared helper or narrowed to a single cast):
- Promote the serverList `toRecord(value: object)` widening helper to
  core/json/jsonUtils.ts and reuse it at core/mcp/node/config.ts (normalize
  loop), core/mcp/remote/node/server.ts (pino level dispatch), and
  clients/web/src/App.tsx (window global lookup).
- inspectorClient.rawWireRequest: type the frame as `JSONRPCRequest` and
  narrow only `params` with a single structural cast (the SDK's `_meta`-typed
  params is what blocked direct assignment).
- toolOutputValidation: SDK `outputSchema` → `JsonSchemaType` is a single cast.
- test-server-fixtures: the optional `task` handle is reachable with a single
  cast (target field is optional).

Justified in place (genuinely unavoidable — private SDK internals, partial
interface stubs, third-party/nominal bridges): the inspectorClient private-map
accesses, resourceContext + tokenAuthProvider partial `OAuthClientProvider`
stubs, the ext-apps peer bridge, modern/legacy `_requestHandlers` bypasses,
and the happy-dom `matchMedia` test mock.

Behavior-neutral. Full `npm run ci` passes (validate, ≥90 coverage gate,
smoke, Storybook).

Refs #1690

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* address @claude review nits: consistent cast justifications + drop reflow noise (#1690)

- test-servers/src/modern-tasks.ts: add an inline justification above the
  `_requestHandlers` double cast, mirroring the sibling in
  composable-test-server.ts (was leaning on the function JSDoc only).
- Annotate the partial-`AppBridge` mock double casts in the story fixtures
  (AppsScreen ×2, AppRenderer, InspectorView) so no non-test-file double cast
  is unjustified.
- inspectorClient.ts: revert unrelated Prettier reflow hunks (protocolVersion,
  task-content array, timeout-reject wrap, reconnect guard) so the diff is the
  single rawWireRequest cast change only.

Behavior-neutral (comment/format-only). `npm run ci` green apart from a known
flaky redaction test whose assertion collided with a random request id.

Refs #1690

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

* actually revert the reflow noise this time (#1690)

The reflow reverts in cc187ea were silently undone by a `prettier --write` I
ran on the same file right after, so the four Prettier-only hunks from 6a3afa4a
were still in the diff (caught in re-review). Revert them for real now — and
without re-running Prettier on the file:

- core/mcp/inspectorClient.ts: restore the protocolVersion line, task-content
  array, timeout-reject call, and reconnect guard to their origin/v2/main form,
  so the file's diff is only the single rawWireRequest cast change.
- test-servers/src/modern-tasks.ts: restore the ModernTaskStatus union to its
  one-line form (the leading-`|` reflow was also Prettier churn), leaving only
  the new `_requestHandlers` justification comment.

Formatting-only; `npm run validate` green.

Refs #1690

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XNdjEPKLG637X8YmhDiEk5

---------

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

core/mcp/remote/node/tokenAuthProvider.ts

@@ -93,6 +93,12 @@ export function createRemoteAuthProvider(
     state() {
       return "";
     },
+    // This provider implements only the members the remote backend transport
+    // exercises (token get/save, client info, non-interactive redirect); the
+    // interactive-only members the SDK never calls on the server side are stubbed
+    // with narrower shapes (e.g. `codeVerifier()` returns `undefined`, not the
+    // interface's `string | Promise<string>`), so it can't be assigned to the
+    // full `OAuthClientProvider` without the double cast.
   } as unknown as OAuthClientProvider;
 
   return {