#23003 cmux-next pane toolbar: the more button is the shared ⋮ overflow button

Leo 2026-10-20: every more button is one shared overflow button, a vertical ellipsis (⋮) like Chrome's, with the same glyph, hit target and hover style. sidebar-cleanup shipped it as OverflowButton in #22972 and switched the sidebar. This PR switches the pane toolbar's more button.

• PaneToolbarView.moreButton is now OverflowButton(label: Strings.paneMore), replacing TitlebarBandButton(symbol: "ellipsis").
• Its menu still opens on mouse-down (pressMenu) and still holds the corner reveal while it is open (presentMenu wrapper).
• VoiceOver's press opens the same menu, so the old openMore action is gone.
• A lit menu still draws in the accent, now through tintOverride.
• Frame, slide and resting opacity are unchanged.

Changelog

• Changed: The pane toolbar's more button is a vertical ellipsis (⋮), like the sidebar's.

Tests

PaneMoreOverflowButtonTests: VoiceOver's press opens the pane's menu, and a lit menu draws in the accent. Existing TabBarRestingControlsTests covers the rest/reveal behavior.

Observed / Not run

• Observed: check-app-size and prepush-gate pass. A fleet run of the suites is running.
• Not run: a live capture of the glyph.

Agent session: cosmic-gray

🤖 Generated with Claude Code

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Summary by cubic

Switches the pane toolbar's more button to the app's shared overflow button (⋮), matching the sidebar's glyph, hit target, and hover style. The menu still opens on mouse-down and keeps the corner revealed while open.

• Replaces TitlebarBandButton(symbol: "ellipsis") with OverflowButton(label: Strings.paneMore).
• VoiceOver's press opens the same menu directly, so the old openMore action is removed.
• A lit menu now draws in the accent via tintOverride instead of contentTintColor.
• Adds PaneMoreOverflowButtonTests covering VoiceOver press and accent tint behavior.