Whole-board copies keep GUIDs — carve-out from the copies-remint rule

Resolves the 01-vs-09/03 contradiction: Save as Template and File ▸
Duplicate copy the board folder as-is, GUIDs kept — the remint rule
governs item-level copies inside an existing board. Duplicate's
fork-keeps-history guarantee requires retention (copied .git history
must keep naming real paths); 03's Duplicate paragraph now says so.

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

DESIGN/01-storage-format.md

@@ -27,10 +27,11 @@ MyBoard.kanban/                                  ← board = the document
 
 - **Level is position.** Root = board, depth 1 = lane, depth 2 = card. No `type` field.
 - **Folder names are lowercase UUIDv4, immutable, never renamed.** The folder name is the primary key; titles live in frontmatter only. Collisions are impossible by construction.
-- **Identity lifecycle: moves keep the UUID, copies mint fresh ones.** Every move (between lanes, between boards, cut+paste) is a physical folder move — identity travels with it. Every copy (⌘C/⌘V, ⌥-drag duplicate, the cross-board drag default — 04-interactions.md's locality model — and template instantiation) mints fresh UUIDs for every folder it materializes; a copy keeps `created` (it's a fork) but is a new identity. **Exception: template instantiation stamps `created`/`modified` fresh** — a board created from a template is born today, not forked from it (09-templates.md); Save as Template, by contrast, is an ordinary fork and keeps timestamps (inert anyway — instantiation restamps them). The app never produces a duplicate UUID: **within-board uniqueness is enforced at the import boundary** — a move-in (a cross-board ⌘-drag move or a cut+paste — 04-interactions.md) whose UUID already exists anywhere in the destination board is degraded to a copy (fresh UUID minted, content intact; the source is removed as usual for a move). **Degradation is per-folder, at the finest grain**: in a compound arrival (a lane with its cards, a multi-card drag or paste), only the colliding folders are reminted — everything else keeps its identity and remains a true move, and source removal is uniform regardless (the whole selection leaves the source, as for any move). A lane drag with one colliding nested card thus stays a lane *move*; just that card arrives reminted. One gesture silently yielding moved originals plus reminted copies is the intended behavior, not an accident — the collision is an identity repair, invisible in content terms. Boards are **independent identity namespaces**: the same UUID may legitimately exist in two boards (e.g. after a cross-board move-out undone at the source — 06-history-undo.md); such forks are tolerated and only ever meet at an import boundary, where the collision is neutralized. A user hand-copying a card folder in Finder can still produce sibling duplicates — the app doesn't currently detect that, and behavior with duplicate sibling-level UUIDs in one board is unspecified.
+- **Identity lifecycle: moves keep the UUID, copies mint fresh ones.** Every move (between lanes, between boards, cut+paste) is a physical folder move — identity travels with it. Every copy (⌘C/⌘V, ⌥-drag duplicate, the cross-board drag default — 04-interactions.md's locality model — and template instantiation) mints fresh UUIDs for every folder it materializes; a copy keeps `created` (it's a fork) but is a new identity. **Whole-board copies are the carve-out**: Save as Template (09-templates.md) and File ▸ Duplicate (03-board-ui.md) copy the board folder as-is, **GUIDs kept** — the remint rule governs *item-level* copies landing inside an existing board, where identities could collide; a whole-board copy is a new namespace, and Duplicate's fork-keeps-history guarantee requires it (copied `.git` history must keep naming the paths it describes). Template GUIDs are inert anyway — instantiation remints at its own boundary. **Exception: template instantiation stamps `created`/`modified` fresh** — a board created from a template is born today, not forked from it (09-templates.md); Save as Template, by contrast, is an ordinary fork and keeps timestamps (inert anyway — instantiation restamps them). The app never produces a duplicate UUID: **within-board uniqueness is enforced at the import boundary** — a move-in (a cross-board ⌘-drag move or a cut+paste — 04-interactions.md) whose UUID already exists anywhere in the destination board is degraded to a copy (fresh UUID minted, content intact; the source is removed as usual for a move). **Degradation is per-folder, at the finest grain**: in a compound arrival (a lane with its cards, a multi-card drag or paste), only the colliding folders are reminted — everything else keeps its identity and remains a true move, and source removal is uniform regardless (the whole selection leaves the source, as for any move). A lane drag with one colliding nested card thus stays a lane *move*; just that card arrives reminted. One gesture silently yielding moved originals plus reminted copies is the intended behavior, not an accident — the collision is an identity repair, invisible in content terms. Boards are **independent identity namespaces**: the same UUID may legitimately exist in two boards (e.g. after a cross-board move-out undone at the source — 06-history-undo.md); such forks are tolerated and only ever meet at an import boundary, where the collision is neutralized. A user hand-copying a card folder in Finder can still produce sibling duplicates — the app doesn't currently detect that, and behavior with duplicate sibling-level UUIDs in one board is unspecified.
 - `index.md` = YAML frontmatter between `---` delimiters, then Markdown body.
 - **Reserved child names** at card level: `attachments/` (specified below) and `comments/` (enhanced schema — see below). Never levels themselves, never identity (identity-bearing siblings are UUIDs).
-- A folder below the root **lacking `index.md` is skipped with a log warning**, not an error — an interrupted two-step create must not brick the board. **Stray tolerance is uniform at every level**: non-reserved files and folders at board, lane, or card level are ignored by the loader, preserved verbatim, never rendered (inside a card, only `index.md` and the reserved child names mean anything — anything else is not the app's business).
+- **Name shape gates level detection** (settled): only folders named as lowercase UUIDv4 are lane/card candidates. Anything else — even with an `index.md` inside — is a stray: skipped with a log warning, preserved verbatim, never rendered. A hand-made `notes/` folder or a board nested inside another can never brick a load; the cost — a hand-authored lane named `todo/` doesn't render — is what the warning and the agent guide exist for.
+- A UUID-named folder below the root **lacking `index.md` is skipped with a log warning**, not an error — an interrupted two-step create must not brick the board. **Stray tolerance is uniform at every level**: non-reserved files and folders at board, lane, or card level are ignored by the loader, preserved verbatim, never rendered (inside a card, only `index.md` and the reserved child names mean anything — anything else is not the app's business).
 - **Atomic writes**: temp file, rename over `index.md`.
 - **Unknown frontmatter keys and their order are preserved verbatim** on every rewrite. This is load-bearing for agent overlays (`project:`, `sphere:`, custom tags) — see 08-agent-integration.md.
 - **The app never reformats a body it didn't change** (byte-identical round-trip; plain string comparison, no re-serialization).