feat(routing): add DISABLE_CONTEXT_WINDOW_CHECKS bypass for the direct-request input/context check (#10927)

Rescoped from #10606 — see PR body for the full rationale (combo-routing half made moot by #10162's advisory-only architecture, chatCore.ts hard-reject bypass retains real value).

Validated in an isolated worktree boarded onto origin/release/v3.8.50:
- 65/65 focused unit tests pass (chatcore-model-output-cap-wiring + feature-flags-settings).
- check-file-size, check-changelog-integrity: OK.
- typecheck:core: clean.
- check-complexity / check-cognitive-complexity: OK, both under baseline.

Co-authored-by: JxnLexn <10897478+JxnLexn@users.noreply.github.com>

src/shared/utils/featureFlags.ts

@@ -72,6 +72,22 @@ export function isCcCompatibleProviderEnabled(): boolean {
   return isFeatureFlagEnabled("ENABLE_CC_COMPATIBLE_PROVIDER");
 }
 
+/**
+ * Context-window checks are fail-safe: an unavailable flag store must never
+ * silently disable local request bounds.
+ */
+export function areContextWindowChecksDisabled(): boolean {
+  try {
+    return isFeatureFlagEnabled("DISABLE_CONTEXT_WINDOW_CHECKS");
+  } catch (error) {
+    console.error(
+      "[featureFlags] Failed to resolve DISABLE_CONTEXT_WINDOW_CHECKS, keeping checks enabled:",
+      error instanceof Error ? error.message : error
+    );
+    return false;
+  }
+}
+
 export function isApiKeyRevealEnabledFlag(): boolean {
   try {
     return isFeatureFlagEnabled("ALLOW_API_KEY_REVEAL");