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>

scripts/typecheck-all.ts

@@ -61,6 +61,39 @@ for (const pkg of packages) {
 }
 
 console.log();
+
+// Step 2 — consumer-strict smoke. Compiles a tiny "as if I were a
+// downstream app" project against our public API surface under the
+// consumer-likely tsconfig (`lib: ["DOM"]` + `exactOptionalPropertyTypes`).
+// Catches type-bugs that ONLY surface when our internal narrower types
+// meet a consumer's standard-library types — the class of bug `tsc`
+// inside our own packages does not see (because our packages compile
+// against `lib: ["ES2022"]` only).
+if (filter.size === 0) {
+  console.log('Consumer-strict smoke (lib: DOM, exactOptional, paths→workspace) ...');
+  const consumerDir = join(ROOT, 'tests', 'consumer-strict');
+  if (existsSync(join(consumerDir, 'tsconfig.json'))) {
+    const proc = Bun.spawnSync(['bunx', 'tsc', '--noEmit', '-p', 'tsconfig.json'], {
+      cwd: consumerDir,
+      stdout: 'pipe',
+      stderr: 'pipe',
+    });
+    const out = (proc.stdout.toString() + proc.stderr.toString())
+      .split('\n')
+      .filter((l) => !/^Resolving|^Resolved|^Saved/.test(l))
+      .join('\n')
+      .trim();
+    if (proc.exitCode === 0 && out.length === 0) {
+      console.log('  ✓ consumer-strict');
+    } else {
+      failures++;
+      failed.push({ pkg: 'consumer-strict', out });
+      console.log('  ✗ consumer-strict');
+    }
+  }
+  console.log();
+}
+
 if (failures === 0) {
   console.log(`All ${packages.length} packages type-check cleanly.`);
   process.exit(0);