chore: address final-review minors — surface event-consumer crashes, document IIFE-wrap heuristic, log shutdown failures, fix CHANGELOG file-size claim

Five tweaks from the whole-implementation review:
- session.ts: log unexpected event-consumer rejections instead of silent swallow
- client.ts: comment the return-substring IIFE-wrap false-positive case
- transport.ts: comment that ws.onclose post-open settle is no-op-by-design
- index.ts: log client.stop() failures during shutdown
- CHANGELOG.md: correct largest-file claim (transport.ts and client.ts are ~220 each, not "client.ts at ~180")

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

5 files changed, 22 insertions, 3 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0dab13d..ffc11e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,7 +6,7 @@ All notable changes to pi-browser-harness will be documented in this file.
 
 ### Internal rewrite
 
-- Per-domain module split: every tool now lives in its own `src/domains/<name>.ts` file. The 1140-line `daemon.ts` and 2277-line `tools.ts` are gone; the largest single file is now `src/client.ts` at ~180 LOC.
+- Per-domain module split: every tool now lives in its own `src/domains/<name>.ts` file. The 1140-line `daemon.ts` and 2277-line `tools.ts` are gone; the three largest files are now `src/cdp/transport.ts` (~220 LOC), `src/client.ts` (~220 LOC), and `src/domains/js.ts` (~200 LOC).
 - New transport/session/client split: `BrowserDaemon` class replaced with `createBrowserClient()` factory composing a `CdpTransport` (factory) and `CdpSession` (factory).
 - All tool handlers now return `Result<T, E>`; one `defineBrowserTool` helper converts to pi's `ToolDefinition` and supplies a uniform `details` shape: `{ ok: true, ... }` on success, `{ ok: false, kind, message, ... }` on error.
 - Strict TypeScript flags enabled (`noUncheckedIndexedAccess`, `exactOptionalPropertyTypes`, `noPropertyAccessFromIndexSignature`, `noUnusedLocals`, `noUnusedParameters`). Zero `any` in the codebase. All boundary `as` casts documented.
diff --git a/src/cdp/session.ts b/src/cdp/session.ts
index fffa241..b1ae71c 100644
--- a/src/cdp/session.ts
+++ b/src/cdp/session.ts
@@ -45,7 +45,13 @@ export const createCdpSession = (transport: CdpTransport): CdpSession => {
   };
 
   const restartConsumer = (): void => {
-    activeConsumer = activeConsumer.then(() => consumeEvents()).catch(() => undefined);
+    activeConsumer = activeConsumer.then(() => consumeEvents()).catch((e: unknown) => {
+      // The .then() chain calls consumeEvents() which iterates the transport's
+      // events() AsyncIterable. The iterable resolves cleanly on close (returns
+      // {done:true}); any rejection here is an unexpected bug in the event
+      // handler, not a normal termination. Surface it on stderr so it's not lost.
+      console.warn("[pi-browser-harness] CDP event consumer crashed:", e);
+    });
   };
 
   restartConsumer();
diff --git a/src/cdp/transport.ts b/src/cdp/transport.ts
index 6da25fa..c5a5a41 100644
--- a/src/cdp/transport.ts
+++ b/src/cdp/transport.ts
@@ -156,6 +156,9 @@ export const createCdpTransport = (): CdpTransport => {
           clearTimeout(timer);
           ws = null;
           cleanup("WebSocket closed");
+          // If onopen already settled the connect promise, this settle is a no-op
+          // (guarded by `settled`). cleanup() above still runs unconditionally so
+          // pending requests are rejected and the event queue is rotated.
           settle(err(cdpError("transport_closed", "CDP WebSocket closed")));
         };
       });
diff --git a/src/client.ts b/src/client.ts
index 1fcef67..51dfa9f 100644
--- a/src/client.ts
+++ b/src/client.ts
@@ -117,6 +117,10 @@ export const createBrowserClient = (opts: BrowserClientOptions): BrowserClient =
   };
 
   const evaluateJs = async (expression: string, sessionId?: string): Promise<Result<unknown, CdpError>> => {
+    // Heuristic IIFE wrap: legacy convenience that lets agents write
+    // `return foo` instead of `(() => foo)()`. False-positive on substring
+    // `"return "` inside string literals or comments — agents that hit this
+    // can pass an explicit IIFE instead.
     const wrapped = expression.includes("return ") && !expression.trim().startsWith("(")
       ? `(function(){${expression}})()`
       : expression;
diff --git a/src/index.ts b/src/index.ts
index f5c7676..ee59f10 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -115,7 +115,13 @@ export default function browserHarnessExtension(pi: ExtensionAPI): void {
   pi.on("session_shutdown", async () => {
     persistState(pi, state);
     if (client) {
-      try { await client.stop(); } catch { /* best-effort */ }
+      try {
+        await client.stop();
+      } catch (e) {
+        // Shutdown is best-effort, but a stuck stop() points at a transport
+        // bug worth surfacing for debugging.
+        console.warn("[pi-browser-harness] client.stop() failed during shutdown:", e);
+      }
       client = null;
     }
     toolsRegistered = false;