fix(provider-usage): close details without hiding gauge

[64ix]

Description

Make the X button in Claude and Codex usage details close only the popover. It no longer disables the corresponding usage gauge setting.

Use the shared PopoverClose primitive and add a browser regression test that verifies the gauge remains visible after closing its details.

Related issues

None.

Testing

• oxfmt --check on the changed files
• oxlint on the changed files
• tsgo --noEmit
• Browser regression test added; not run locally because the environment denied the Vitest loopback listener with EACCES

Screenshot/Recording (if applicable)

Not included; this restores the expected close-button behavior without changing the visual layout.

Checklist

• I kept this PR small and focused
• I ran a self-review before opening this PR
• I ran the relevant local checks or explained why not
• Documentation is not required for this behavior correction
• I added a regression test
• I only added comments where the logic is not obvious
• I used Conventional Commits for the commit message and PR title