computer tool's screenshot/find/read_page/scroll consistently timeout with "document_idle" wait failure across ALL pages

## Description
Starting this morning, the `computer` tool's `screenshot`, `find`, `read_page`, and `scroll` actions consistently fail with a "document_idle" wait timeout (5s for screenshot, 45s for find/read_page), on EVERY page tested, not just one site.

## Reproduction
1. Navigate to any URL (tested: google.com, ebay.com, example.com, crowdworks.jp)
2. Call `computer` with action=`screenshot`, or `find`, or `read_page`, or `scroll`
3. Result: "Script injection timed out" or "Page still loading (executeScript waited 45000ms for document_idle)", every time, on a fully-loaded, idle page

## What still works
- `javascript_tool` (javascript_exec) - instant, reliable
- `navigate` - works fine
- `computer` action=`type` - works fine

## What is broken
- `computer` screenshot/find/read_page/scroll - always times out
- `computer` left_click/key - report success but do NOT actually deliver events to the page (verified via before/after DOM state checks; only a JS-triggered `.click()` via javascript_tool actually works)

## Investigation done
- Confirmed NOT page-specific: fails identically on google.com, example.com, ebay.com, crowdworks.jp
- Confirmed NOT network-related: checked `read_network_requests`, zero pending requests on the affected tab
- Tried: bringing the Chrome window to the foreground, restarting Chrome, fully quitting and restarting the Claude Code desktop app, toggling macOS Screen Recording permission off/on, new tabs, new tab groups - none of these fixed it
- This persisted across a full app + browser restart, which rules out simple local process state
- The day before, the exact same kind of browser automation (eBay listing creation/editing) worked completely normally, so this is a regression, not a pre-existing limitation

## Environment
- macOS, Claude Code desktop app
- Claude in Chrome extension (mcp__claude-in-chrome__* tools)

## Impact
Blocks any task that needs precise clicking, element lookup, or file upload via a file input (which requires a `ref` from `find`/read_page`). Has been blocking real e-commerce listing work for a full day.

Start by reproducing the timeout with the computer screenshot, find, read_page, and scroll actions on a simple page, then compare them with javascript_tool and navigate. Done means those actions no longer fail with document_idle or script-injection timeouts and left_click/key events reach the page; the payload names no source files or tests to inspect.

Written by the indexing model from the issue text.