History trail starts fresh for repo reasons, not identity reasons

Fixes 05's rationale: a cross-board move keeps its UUID (remint is
collision-only); the listing starts fresh because the destination repo
has no commits for the arriving folder.

Claude-Session: https://claude.ai/code/session_01HJ7PhFNmQ19bvy9RMD6GSb

DESIGN/05-card-window.md

@@ -73,7 +73,7 @@ The card-level styling home: the **embedded style editor** — background palett
 ### History (git boards only)
 
 - **The card's commit trail, read-only** (settled): every commit that touched this card's folder, newest first — semantic subject, relative date, author. The trail is where the commit-message and attribution machinery (06-history-undo.md) pays off for humans: "Move card 'X' to Doing — 2 days ago — Claude" reads as a story, agent and hand edits included (foreign authorship and `modified-by` refinement render as the author).
-- The listing **follows the card across lane moves** (path changes; the UUID folder is the identity to track). A cross-board arrival starts fresh — the import boundary remints identity (01-storage-format.md), and the old board keeps the old trail.
+- The listing **follows the card across lane moves** (path changes; the UUID folder is the identity to track). A cross-board arrival starts fresh — not because identity changes (a move keeps its UUID; the import boundary remints only on collision — 01-storage-format.md) but because the destination board's repo has no commits for the arriving folder; the old board keeps the old trail either way.
 - The section is **absent** on boards without app-managed git (mode none, repo-nested) — same honesty rule as the popover's git section (06-history-undo.md). Rows are focusable (arrows), but carry **no actions in v1** — restoring an old version stays a git-client task for now; a per-row forward-restore and lane history are wishlist items, deliberately.
 - Menu path (contract): **View ▸ History** in the card window focuses the section — no default chord.