Tool window: tabs across the four views, maximize, one rail

[thethinkmachine]

The window that Library, Algorithms, Grammar and Reference share had a title bar that only named the open view and offered a close button. To get from one view to another you had to close the window and reopen it from the More menu. This PR turns the window's bar into a tab strip and makes the four views look like parts of one window.

What changed

Tab strip in the bar. The bar now holds four tabs, in this order: Library, Algorithms, Grammar, Reference.

• The tabs are built from AUX_META, so each view's name and icon are defined in one place.
• Only the selected tab is a Tab stop (roving tabindex), and Arrow/Home/End move between tabs.
• Each view's old subtitle is now that tab's tooltip, along with its shortcut key.
• None of the bar's controls are added to bridge.js.

Shortcut keys follow the tab order. AUX_VIEWS sets the order for the strip, the More menu's Explore group and the number-key shortcuts. auxViewKey() works out each view's key from its position. Because Library moved to the front, the keys change: Library is now 2, Algorithms 3, Grammar 4, Reference 5. Before, they were Algorithms 2, Grammar 3, Reference 4, Library 5.

Maximize.

• A new button toggles the window between its normal size and nearly the full screen, with a 12px margin. It reports its state with aria-pressed.
• Double-clicking an empty part of the bar does the same.
• The choice is remembered per reader in automata-aux-max. It is desktop only, since below 900px the window is already full-screen.
• There is no minimize button: every view already keeps its place when you close the window.

Which machine Algorithms will use. While Algorithms is open, the bar shows the machine on the canvas, for example DFA · 5 states · 7 transitions. The canvas is hidden behind the window, so this was otherwise only visible after closing it.

One shape for the four side menus. They were 200, 208, 190 and 190px wide (two set with inline styles) and used two different fonts, so the menu's edge jumped when switching between views. They now share one width (--aux-rail-w), one row style in sans, and one group-heading style.

Smaller fixes

• The close button no longer turns red on hover. Its tooltip now says "Back to canvas — this view keeps its place".
• The "Reference" tab drops the word "Automata".
• Messages telling you to "build an automaton first in the Build tab" pointed at a tab that no longer exists. They now say "Draw … on the canvas first" and offer a Back to canvas button.
• On phones, the tabs show icons only, plus the name of the active tab.

Testing

• npm test: 2621 passed, 0 failed. This includes the new tests/aux-window.test.js, which covers the tab order and selection, the arrow keys, Library being first with the More menu and keys in the same order, maximize being remembered, the machine label, and the single menu width.
• npm run build succeeds.
• Checked in Chromium at 1440×900 and 390×844: no page errors, the 2 key opens Library, and maximize persists across reloads.

Worth trying by hand: switching between tabs on a machine you've built, maximize on a large monitor, and the new number keys. If you'd rather keep the old key numbers, I can revert that part.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HPVKDwzQWjyqE1nApBQt6s

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Generated by Claude Code

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