feat(web): put panel tab close buttons after the title

[alexandre-vl]

Problem

Hovering a right-panel tab or a terminal-list row swaps its icon for the close button, so close sits left of the title.

Change

• The icon stays put and the close button follows the title, in the right panel and the terminal list.
• Inactive tabs: the × floats over the end of the title on hover or keyboard focus, with a short fade, so hovering never changes a width.
• Active tab and active terminal row: the × stays visible in its own space, so a tab grows by up to 10px when it becomes active.
• A 64px min tab width keeps short titles clickable. A terminal running vi is labelled "vi", 9px wide.
• Touch screens always show the ×, like the floating stop button in ThreadRelationshipsControl.
• Mute, panel-level close and the add-surface menu are unchanged. Terminal observers still get no ×.

Scope and approval

Approved in #17986 (converted from #11877): #17986 (comment), "Target the VS Code-style row: [icon] [title] [× on hover]", optionally in the terminal list too.

Two choices go beyond that row: the active tab keeps its × visible, and the 64px min width. Happy to drop either.

Written from scratch on current main. Supersedes #12062, which was closed in the PR cleanup.

Verification

Dev build, headless Chrome:

• A click on the middle of each title switches tabs. "Diff" clears the × by 13px and "vi" by 18px.
• The × closes only its own tab, middle-click still closes, drag reorder works, and hovering never changes a width.
• Keyboard: Tab from a title focuses its ×, which shows, and Enter closes the tab.
• Touch (emulated): every × shows without hover, and one tap on a terminal's × opens the close prompt.
• A client without terminal:operate sees no × and no fade.
• vp fmt, vp lint, web typecheck, and the RightPanelTabs / ThreadTerminalDrawer tests (40) pass.

	Before	After
Right panel, hovering Terminal 1
Terminal list

Model: claude-opus-5-5 · Harness: Claude Code

[macroscopeapp]

Approvability

Verdict: Approved at 045788a

Macroscope's review found this PR approvable — This is a localized UI adjustment that repositions and refines visibility of existing panel and terminal close controls while preserving their callbacks, permissions, and close workflows. It introduces no schema, configuration, infrastructure, security, billing, or static-analysis changes.

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[juliusmarminge]

Note

This comment is posted by Julius' dot

Closing for now: the approved scope keeps close hover/focus-revealed, but this PR makes it permanently visible on active tabs and terminal rows. Please keep that behavior within the approved scope or get approval for the change under the contribution guide. The screenshots show the layout, but the changed hover, keyboard-focus and touch interactions also need a short recording. Address those points and request reconsideration.

[alexandre-vl]

Addressed both points in #18206: close is now hover/focus-revealed on every tab and terminal row, active ones included, and the PR has recordings of the hover, keyboard and touch interactions.