feat(style): a preview button that shows its state, a quiet search, and an icon on every tab (#308)

[Maxaubert]

Closes #308

What

• A3 preview button (BrowseIcon.tsx PreviewGlyph, FolderBrowser.tsx): the pane icon's right column is solid while the preview is open and empty while it is hidden. No accent and no background in any state; hover and focus as Back and Refresh. aria-pressed and the name "Preview pane" are unchanged. It is the only preview toggle in the app.
• B search button (browse.css, FolderBrowser.tsx): the accent rule for [data-active] is gone, so it stays grey while the popup is up and while the list shows a search. data-active stays as a mark for tests.
• C2 tab icons (TabKindIcon.tsx, TabStrip.tsx): every tab shows what it holds. Explorer tabs (pinned or not, Downloads-style included) get a folder, project tabs code brackets, Settings a gear. Solid on the active tab, lines on the rest, in the tab's own ink. The solid code tile's brackets are cut out with a mask, so glass and the agent's Full fill show through. This replaces the small folder-coloured glyph that only Explorer tabs had. The pin and the close button are unchanged, and the Full indicator's brain slot is still on project tabs.
• Version 0.93.0, and a CLAUDE.md rule quoting the owner (2026-10-06 and 2026-10-07: "A3 and C2").

Why

Owner, 2026-10-07, choosing from research/prism/2026-10-06-new-themes/toolbar-options.html: "A3 and C2". Before that: "i dont like the look of the buttons being colored ... default icons per type of page explorer, project and settings".

Gates

• typecheck: clean. lint: 0 errors (7 old warnings). vitest: 170 files, 2526 tests passed.
• e2e, run one at a time: toolbarIcons 243 checks, addressField 23, searchPopup 48, previewClears 21, panelsAlign 49, tabs 40, titleBar 25, settingsLook 189, sidebarGround 14. npm run e2e:terminal: 553 checks, all passed.
• I ran the new toolbarIcons scenario against main's src and it failed 169 checks: the accent preview and search buttons, no glyph state, and no icons on project and Settings tabs.
• I checked the screenshots in Void and Paper: the toolbar open, hidden and searching, and the tabs in Dynamic and Fixed widths with the Explorer, a project and Settings each in front.

Note

This may conflict with the open PRs #305 and #307 in BrowseToolbar.tsx / browse.css.

🤖 Generated with Claude Code

https://claude.ai/code/session_01FHHaWKR4M5QtW7Wecyuk4t