Reset pinned tabs on close, and add a recent-order close setting

[matthewdias]

What changes

Closing a pinned tab resets it, as Arc does. Top Tabs: Close tab used to do nothing on a pinned tab, and bb's own Close on that page opened New Thread and left the pin where it was. Both now:

• keep the tab pinned;
• forget where it was left, so it next opens at the panel's start;
• move past the other pins, as VS Code skips pinned editors on a keyboard close: to the first ordinary tab, or Threads if there is none. Pressing the shortcut again then closes an ordinary tab instead of stepping through every pin.

⌃⇧T undoes a reset, taking the pin back to where it was, until you go back to the pin yourself. That takes the reset as it is, so a much later ⌃⇧T can't pull the pin back to an old page.

The tab's ×, middle-click, close-others and close-to-the-right still leave pins alone.

New setting: "After closing a tab, go back to the last one you used" (off by default). On, closing the tab in view returns to the tab in view before it, Threads included, like VS Code's focusRecentEditorAfterClose. It reads the strip's existing recent list and falls back to the right-hand neighbour once nothing it remembers is still open. It covers every single-tab close (×, middle-click, context menu, bb's page Close, the command), and leaving a pin follows it too.

How

• lib/tabs-model.ts: successorAfterClose takes a CloseOrder. New successorAfterPinClose, resetPinned and pageCloseAction; closeCommandAction now shares pageCloseAction, so the button and the shortcut cannot drift apart.
• components/TopTabs.tsx: closePinned, and bb's page Close routes pins to it. While the strip leaves a reset pin, a resetting ref stops the location effect from recording the old path again on the way out.
• Reset undo: resetPinned puts the old location on closed as an entry marked reset; reopen gives a reset pin its path back instead of a new slot, and recordPath drops the entry once you revisit the pin. The menus' "Reopen closed tab" now asks the same reopenable as reopen.
• server.ts: the recentAfterClose setting. README and PLUGIN_OVERVIEW are updated.
• Bumps Top Tabs to 0.2.0.

Testing

• npm test (77 pass) and npm run typecheck, npm run build in plugins/top-tabs.
• Mutation-checked: each new rule was broken on purpose (no recent branch, pins not skipped, closed tabs not filtered, the command or bb's Close turned off on pins, unpinned tabs reset, a truthy setting value; for the undo: reset not remembered, the marker ignored, a revisit keeping the entry, the marker lost or loosened on reload, a reset reopened as a new slot) and every mutant failed a test.
• Linked into bb from the branch: the pinned close and the setting were tried by hand. The ⌃⇧T undo is covered by tests and is live in the linked install, but has not been tried by hand yet.

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