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>

tests/consumer-strict/tsconfig.json

@@ -0,0 +1,45 @@
+{
+  "compilerOptions": {
+    "target": "ESNext",
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "strict": true,
+    "noUnusedLocals": false,
+    "noUnusedParameters": true,
+    "noImplicitOverride": true,
+    "exactOptionalPropertyTypes": true,
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "noEmit": true,
+    "types": ["bun-types"],
+    "ignoreDeprecations": "6.0",
+    "baseUrl": ".",
+    "paths": {
+      "@shade/core": ["../../packages/shade-core/src/index.ts"],
+      "@shade/proto": ["../../packages/shade-proto/src/index.ts"],
+      "@shade/crypto-web": ["../../packages/shade-crypto-web/src/index.ts"],
+      "@shade/observability": ["../../packages/shade-observability/src/index.ts"],
+      "@shade/keychain": ["../../packages/shade-keychain/src/index.ts"],
+      "@shade/key-transparency": ["../../packages/shade-key-transparency/src/index.ts"],
+      "@shade/storage-sqlite": ["../../packages/shade-storage-sqlite/src/index.ts"],
+      "@shade/storage-postgres": ["../../packages/shade-storage-postgres/src/index.ts"],
+      "@shade/storage-encrypted": ["../../packages/shade-storage-encrypted/src/index.ts"],
+      "@shade/streams": ["../../packages/shade-streams/src/index.ts"],
+      "@shade/transport": ["../../packages/shade-transport/src/index.ts"],
+      "@shade/transport-bridge": ["../../packages/shade-transport-bridge/src/index.ts"],
+      "@shade/transport-webrtc": ["../../packages/shade-transport-webrtc/src/index.ts"],
+      "@shade/server": ["../../packages/shade-server/src/index.ts"],
+      "@shade/inbox-server": ["../../packages/shade-inbox-server/src/index.ts"],
+      "@shade/inbox": ["../../packages/shade-inbox/src/index.ts"],
+      "@shade/transfer": ["../../packages/shade-transfer/src/index.ts"],
+      "@shade/files": ["../../packages/shade-files/src/index.ts"],
+      "@shade/recovery": ["../../packages/shade-recovery/src/index.ts"],
+      "@shade/observer": ["../../packages/shade-observer/src/index.ts"],
+      "@shade/dashboard": ["../../packages/shade-dashboard/src/index.ts"],
+      "@shade/sdk": ["../../packages/shade-sdk/src/index.ts"],
+      "@shade/widgets": ["../../packages/shade-widgets/src/index.ts"]
+    }
+  },
+  "include": ["./*.ts"]
+}