fix(stats): handle trust prompts and report failed refreshes

[abasiri]

When Claude's workspace trust dialog defaults to “No, exit,” Switchboard's stats refresh sends Enter and exits before updating the cache. The Stats tab then displays the old data without reporting the failure.

Select Yes explicitly: send Down when No is highlighted, wait for the Yes selection to render, then send Enter separately. Preserve compatibility with older dialogs already selecting Yes. Handle fragmented terminal output, clean up pending input and timers, and share overlapping refresh requests.

Report early exits, timeouts, unreadable caches, and an unchanged outdated cache in the Stats tab while retaining cached charts and independent usage data. An unchanged cache covering yesterday is accepted because Claude computes today's activity separately.

Fixes #92

Validation:

• npm test with the existing local dependencies via NODE_PATH: 221 passed, 0 failed or skipped, including 22 new tests for trust handling, failure paths, cache freshness, and the renderer.
• Tested the production helper against Claude Code 2.1.263 on macOS, using Switchboard's home-directory launch and terminal settings. It automatically sent Down, confirmed Yes, and reached the stats display. An already-current cache with unchanged mtime correctly produced no error.
• Syntax checks and git diff --check passed. Electron GUI and Windows/Linux runtime behavior were not tested locally.