refactor: close the remaining unguarded type assertions

Types the event-queue iterator's TReturn as undefined so the terminal
result needs no cast; declares the isError field the pi runtime reads by
duck-typing; binds socket to a local const in the daemon transport;
replaces the @ts-ignore on the optional sharp import with a non-literal
specifier so src/ still typechecks where sharp was not installed.

Adds src/util/guards.ts as the single home for narrowing over unknown —
isRecord plus scalar/array readers — and converts the two private
isObject copies in cdp/types.ts and daemon/protocol.ts along with every
inline `as Record<string, unknown>` in domains/js.ts and domains/render.ts.

Gives Accessibility.getFullAXTree a real result schema, closing the last
unvalidated CDP boundary: only nodeId is required, every object carries
additionalProperties, and each AX value stays Unknown, so the tree
decodes as a whole or fails as a whole rather than being filtered.

Guards the five tool-result `details` readers, the daemon attach
response, the persisted session state, the browser-namespace flag, and
the fs errno narrowing, each feeding an already-present failure path.

The daemon-transport socket binding is not a bug fix: send() runs
synchronously inside sendWithTimeout's promise executor, so socket cannot
be reassigned between the check and the write. It removes the assertion
and makes the write immune to a later refactor that adds an await.

Two assertions survive by design and are documented in the task report:
the never->unknown re-widening in util/tool.ts, which the type-erased
tool registry makes unavoidable, and the AsyncFunction constructor lookup
in domains/js.ts, which JavaScript exposes no typed binding for.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/src/cdp/types.ts b/src/cdp/types.ts
index d57255f..33ab202 100644
--- a/src/cdp/types.ts
+++ b/src/cdp/types.ts
@@ -1,3 +1,5 @@
+import { isRecord } from "../util/guards";
+
 export type CdpEvent = {
   readonly method: string;
   readonly params: unknown;
@@ -51,11 +53,8 @@ const INTERNAL_PREFIXES: ReadonlyArray<string> = [
 export const isInternalUrl = (url: string): boolean =>
   INTERNAL_PREFIXES.some((p) => url.startsWith(p));
 
-const isObject = (v: unknown): v is Readonly<Record<string, unknown>> =>
-  typeof v === "object" && v !== null && !Array.isArray(v);
-
 export const isCdpRawMessage = (v: unknown): v is CdpRawMessage => {
-  if (!isObject(v)) return false;
+  if (!isRecord(v)) return false;
   const id = v["id"];
   if (id !== undefined && typeof id !== "number") return false;
   const method = v["method"];
@@ -64,7 +63,7 @@ export const isCdpRawMessage = (v: unknown): v is CdpRawMessage => {
   if (sessionId !== undefined && typeof sessionId !== "string") return false;
   const errVal = v["error"];
   if (errVal !== undefined) {
-    if (!isObject(errVal)) return false;
+    if (!isRecord(errVal)) return false;
     if (typeof errVal["message"] !== "string") return false;
     const code = errVal["code"];
     if (code !== undefined && typeof code !== "number") return false;