Expose `upload_file` in Compact mode

[esokullu]

Problem

Compact Act tier does not expose the upload_file tool in either the Chrome or Firefox build. The native file-picker guard can prevent an orphaned OS dialog, but a Compact agent cannot recover from the blocked click by switching to a direct upload.

A duplicate search found no similar open issue.

Proposed direction

• Add only upload_file to the Compact tool set in both browser builds.
• Add concise Compact prompt guidance:
  • When a file input already exists, upload directly without clicking the page upload control.
  • If a lazy widget creates its input only after initialization, allow one guarded initializer click and then retry with the exact selector.
  • Never substitute a generic input[type="file"] selector when multiple file inputs exist.
• Give Compact a tool description that does not recommend unavailable download_files or list_downloads tools.
• Keep broader download/list workflows out of this issue so the Compact decision surface grows by only one tool.

Acceptance criteria

• getToolsForMode('act', { tier: 'compact' }) returns upload_file in both Chrome and Firefox.
• Ask mode and the remaining Compact tool boundaries are unchanged.
• Compact prompt and tool-description behavior stay aligned across both browser builds.
• Tests cover the Compact tool surface, direct-upload guidance, and the guarded lazy-widget retry contract.

Scope

This issue is intentionally upload-only. Adding download_files, list_downloads, or a broader Compact file workflow should be evaluated separately.

[esokullu]

not sure!