Browser pane: file:// tabs render as static snapshot but cannot be read/screenshotted by any tool

Summary
When navigate (or preview_start) is pointed at a local file:// URL for a file outside the project working directory, the tool response says it opened "in the preview pane (files outside the project folder render as static snapshots)", and the tab appears correctly in tabs_context with the right origin. The content is visibly rendered in the user's GUI (confirmed directly by the user). However, every tool that should be able to read that tab's content fails identically:

• computer (action: "screenshot") -> Error: No site is open in this tab. Use navigate first.
• get_page_text -> same error
• read_page -> same error

This happens even immediately after a successful navigate call to that exact tabId, and even when the tab is the active tab.

Repro

1. Have a local file (tested with a multi-page PDF) located outside the current project/working directory.
2. Call navigate with a file:///... URL pointing at it and a fresh tabId (from tabs_create).
3. Tool responds with the "renders as a static snapshot" caveat and lists the tab correctly in tabs_context.
4. Call computer with action: "screenshot" and the same tabId -> fails with "No site is open in this tab."
5. Same failure for get_page_text and read_page.

Impact
This creates a confusing capability gap: the tool's own response implies content is being displayed to the user, and the user can visually confirm it's on their screen, but the assistant has no way to inspect, screenshot, or extract any of that content. Concretely, this blocked extracting figure/image content from a local PDF manual that was visibly open in the pane.

Two possible fixes:

1. Make computer/get_page_text/read_page actually work against "static snapshot" tabs (at least screenshot, since it is a rendered image already).
2. If that is fundamentally not supported, have navigate/preview_start say so plainly (e.g. "this will display for the user but cannot be read back by any tool"), rather than a response that reads as if the page loaded normally.

Environment

• Claude Code CLI on Windows 11, the Browser pane tool family (Claude_Browser MCP tools).
• Reproduced with a local PDF opened via file://, both from a temp directory and from inside the project working directory tree.