fix(web): keep workspace card action hover uniform

[Bil0000]

Workspace card split actions added a second background when hovering their right-hand button. Keep both halves transparent so the row supplies one hover color, matching the branch selector. Apply the same shared style to PR checks.

Covers editor, project script, Git, PR action, and lineage split controls in the inline card and popover. This changes panel styles only; toolbar controls and action behavior stay the same.

Verified: 123 focused tests, web typecheck and build, targeted lint and formatting. Checked hover and pressed backgrounds in the real app in dark/light themes, at 1280px and 900px, and opened the action menus. The fixture did not expose every PR/lineage state; those use the shared styles reviewed here.

Before and after show the same Actions arrow hover. Other app content is hidden and the card is enlarged for clarity.

Before	After

Model: GPT-6. Harness: Codex.

[macroscopeapp]

Approvability

Verdict: Approved at eeab10c

Macroscope's review found this PR approvable — This is a narrowly scoped visual fix that standardizes hover and pressed backgrounds for existing thread-details controls without changing interaction behavior or broader product defaults. The remaining comment requests a component-variant refactor for consistency but does not identify a functional defect.

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