The board popover goes tabbed — Info, Background, Git, three empty rooms awaiting their own sessions

The symbol/name header keeps the top; below it a segmented tab bar replaces
the styling embed and the git section, both parked in-file — their seams are
settled, test-pinned design, and the tab sessions rehome surfaces, not rulings.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

DESIGN/03-board-ui.md

@@ -53,6 +53,8 @@ One **style editor** component — a background palette grid and a curated symbo
 
 ## Board popover
 
+**Restructure in progress (2026-08-07): the popover is going tabbed.** The symbol/name header stays at the top; below it sit three tabs — **Info**, **Background**, **Git** — each the settings surface for one aspect of board configuration, each to be designed in its own dedicated session (all three are empty placeholders until then). The bullets below describe the popover's pre-tab content; what of it rehomes into which tab — and where the embedded style editor lands — is those sessions' to settle. The rulings inside the bullets (rename semantics, the git postures, the popover/sheet split) stand; only their placement is in motion.
+
 The window-title widget opens the **board popover** — the one board-level surface, hosting:
 
 - **Board rename** (settled: this function stays in-app, unlike the pathfinder which dropped it with the inspector). Rename edits the board's frontmatter `title` only — the folder is never renamed by the app; the Finder document name is Finder's to change (01-storage-format.md's board-naming rule). A foreign rename landing while the popover is open resyncs the field from the snapshot only while the field is unfocused — a focused field keeps the user's keystrokes, the dirty-buffer courtesy applied here (settled).