Name the EchoLedger in 02 — settle write provenance for attribution and announcements

06 and 10 consumed a per-file app-vs-foreign classifier that 02's component
inventory never named and whose layering prose seemed to deny. Settled: a
new EchoLedger component records each BoardWriter operation's expected
outcome (content hash / absence / move pair); final-content matching
classifies each observed file, deciding both races (byte-identical foreign
write → app-mediated, accepted; same-window foreign overwrite → foreign,
last writer wins). Ledger is in-memory and per-store; launch catch-up is
all-foreign; bracketed operations bypass it. "Trusts its own writes no more
than anyone else's" is scoped to rendering; BoardWriter's no-hidden-state
bullet stands.

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

DESIGN/02-architecture.md

@@ -20,7 +20,7 @@ BoardStore (one per open board, @Observable, MainActor)
 SwiftUI views (board window + card windows share the store)
 ```
 
-One-way flow: **files → watcher → loader → store → views**. User actions go through a Writer that mutates files; the change comes back around through the watcher like any external edit. The app trusts its own writes no more than anyone else's — this is what makes external editors and agents first-class.
+One-way flow: **files → watcher → loader → store → views**. User actions go through a Writer that mutates files; the change comes back around through the watcher like any external edit. The app trusts its own writes no more than anyone else's — **for rendering** (settled scope): the snapshot is only ever built from disk, never from memory of what the app meant to write — this is what makes external editors and agents first-class. Provenance is a separate, downstream concern: the **EchoLedger** (Components below) remembers what the app wrote so commit attribution (06-history-undo.md) and VoiceOver announcements (10-accessibility.md) can tell the app's own echo from a foreign change — without the render path ever trusting memory over disk.
 
 The **one named exception** is transient UI state rendering things that don't exist on disk — concretely the **new-card placeholder** (04-interactions.md): the inline editor for a card being created renders as a pseudo-card overlaid on the snapshot, with no disk presence and no UUID until the title commits. Commit creates the folder through the Writer and round-trips through the watcher like any write — the placeholder stays visible until the real card arrives, then hands off. Abandoning (Escape, empty commit, click-away) discards it; disk was never touched. Watcher reloads swap the snapshot *underneath* the overlay (like selection surviving a reload); if the placeholder's lane vanished in the reload, it is discarded — consistent with card windows dismissing when their card is deleted. Everything durable still round-trips through files.
 
@@ -28,7 +28,8 @@ The **one named exception** is transient UI state rendering things that don't ex
 
 - **Frontmatter** — YAML value model: parse, serialize, atomic write, unknown-key preservation with key order. Owns the byte-identical round-trip guarantee. Pure, heavily unit-tested.
 - **BoardLoader** — walks the folder tree, applies the fail-fast/skip rules, produces an immutable `BoardModel` snapshot. Pure function of the tree.
-- **BoardWriter** — every mutation (create, move, reorder, tombstone, style) as an explicit filesystem operation. No hidden state; a write is done when the file is on disk.
+- **BoardWriter** — every mutation (create, move, reorder, tombstone, style) as an explicit filesystem operation. No hidden state; a write is done when the file is on disk. (The EchoLedger's receipts are not this bullet's "hidden state": a receipt describes a *completed* write, and the ledger lives beside the Writer, not in it — no write is ever pending in memory.)
+- **EchoLedger** — the write-provenance ledger (the "Writer/echo machinery" that 06-history-undo.md ▸ Commit attribution and 10-accessibility.md ▸ Live board announcements consume; settled). Every BoardWriter operation drops a receipt of its expected on-disk outcome before returning: path → content hash for writes (attachment imports hash during the copy — the bytes stream through the app anyway), an absence marker for deletes, an old→new pair for folder moves; a newer app write to the same path supersedes the receipt. Classification runs per observed changed file in a debounce window: current on-disk content matches the receipt → **app-mediated**, receipt consumed; no receipt, or mismatch → **foreign**. Final content deciding is what settles the races: an agent writing byte-identical bytes over a fresh app write matches and classifies app-mediated — with identical bytes the misattribution is unobservable in the tree, accepted; a foreign edit landing on an app-written path inside the same window misses the hash and the file classifies foreign — last writer wins the file, the app's subsumed intermediate never separately recorded (the diff compares snapshots, not a journal — 06-history-undo.md). Consumers: the auto-committer's author field and two-commit split (06), and the announcement filter (10) — on no-git boards the ledger runs identically with the announcer as its only consumer. **In-memory, per-store, dies with the session** — losing it costs attribution and nothing else, so the launch catch-up commit (06) classifies everything foreign: the app never vouches for changes it didn't witness. Bracketed operations don't consult it (they commit themselves and announce once at completion), and the reload-granularity origin tag (Live-reload resilience below) is orthogonal: it classifies *reloads*, the ledger classifies *files*. Feeds attribution and announcements only — never the render path (Layering above).
 - **BoardStore** — per-board `@Observable` object holding the current snapshot plus transient UI state that must be shared across that board's windows (selection, drag state, search query, pending cut, the new-card placeholder, trash visibility). Coalesces watcher reloads — at most one tree walk in flight, signals landing mid-walk fold into one follow-up; the debounce itself lives in FolderWatcher (above).
 - **BoardStoreRegistry** — refcounted registry so a board window and its card windows share one live store and one watcher. **The board window owns the board** (settled): card windows never outlive it — closing the board window closes its card windows too, so the last-window teardown and board-window close coincide. (The refcount still earns its keep ordering teardown while multiple windows close.)
 - **FolderWatcher** — FSEvents (debounced: **200 ms trailing**, the timer restarting per event so a burst yields one reload after quiet, over 50 ms FSEvents latency — settled numbers), attached best-effort to whatever path the board lives at. **Events under any `.git` path component are filtered out** (settled): the board's own root-level repo (a worktree-link `.git` file included) is the app's auto-commit churn, and a repo nested deeper — a card folder containing a clone, a submodule — is a stray (01-storage-format.md) whose internals never render; neither can alter the rendered tree, so neither drives reloads. (A nested repo's *working files* still fire events like any stray's — those reloads are value-equal and quiet.) There is only this one watching path: no NSMetadataQuery for iCloud Drive, no polling fallback for network volumes — on those warned-against locations (07-sync-collab.md) FSEvents delivery is unreliable and live reload silently degrades, accepted per 07's no-accommodations stance.