release(v4.0.2): consumer-strict reader-shape fixes

4.0.1's typecheck gate compiled each package internally against
lib: ["ES2022"]. That doesn't catch types that only fail when
*consumer* code (lib: ["DOM"] + exactOptionalPropertyTypes) tries to
assign a native browser type into one of our locally-defined narrower
types. Dispatch hit one such case in @shade/files inline-threshold.ts.

This release adds a tests/consumer-strict/ smoke project to the
pre-publish gate. It compiles a tiny "as if I were a downstream app"
TS file against:

  lib: ["ES2022", "DOM", "DOM.Iterable"]
  types: ["bun-types"]
  exactOptionalPropertyTypes: true
  strict: true
  paths → packages/*/src/index.ts

scripts/typecheck-all.ts now runs the smoke after per-package checks.
Both must pass before publish:dry / publish:all proceeds.

### Fixed
- @shade/files inline-threshold.ts: MinimalReader<T> rewritten as the
  explicit disjoint union { done:false, value:T } | { done:true,
  value?: T | undefined } that's assignable from every native reader
  shape (bun, DOM, node:stream/web). Fixes the
  "ReadableStreamReadResult is not assignable" Dispatch reported.
- @shade/files streams-bridge (client + server): stash setTimeout
  return in a local before .unref?.() via { unref?: () => void } cast.
  Fluent .unref?.() failed under lib: ["DOM"] (setTimeout returns
  number there).
- @shade/sdk background.ts: same setInterval .unref?.() fix.

Wire-compatible. No API shape changed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-files/src/client/streams-bridge.ts

@@ -142,13 +142,14 @@ export async function createClientStreamsBridge(
     }
 
     parked.set(readStreamId, arrival);
-    setTimeout(() => {
+    const t = setTimeout(() => {
       const stale = parked.get(readStreamId);
       if (stale === arrival) {
         parked.delete(readStreamId);
         void handle.abort('rpc-timeout').catch(() => undefined);
       }
-    }, parkedReadTtlMs).unref?.();
+    }, parkedReadTtlMs);
+    (t as unknown as { unref?: () => void }).unref?.();
   });
 
   function cleanupWaiter(w: PendingReadWaiter): void {