Memoize the reload parse and short-circuit value-equal snapshots

The loader gains a ParseMemo — the previous walk's parsed documents keyed
by root-relative path, trusted on the git-index heuristic (mtime + size,
no hashing) and passed as an input so the loader stays stateless. A hit
skips exactly one file read; schema, order, coercions, dedupe, and every
directory listing run fresh, so memoized and cold walks are output-
identical (golden-corpus equivalence suite). Entries record only past the
schema gate, so a defect can never be answered from the memo.

The store skips the snapshot assignment wholesale when the fresh model is
value-equal — no @Observable churn, no render pass, no snapshotGeneration
bump — and a new landedReloads counter carries walk-completion for the
three consumers whose subject is the walk, not the snapshot: the card
window's comment thread, the comment search index, and the auto-committer's
covering gate (which now counts a completed walk as covering even when
nothing changed). Warnings and defects move on their own equality; failed
reloads bump neither counter. An injectable ParseCounter makes the
single-file-echo claim a test.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97

Kanban/App/AppModel.swift

@@ -889,8 +889,13 @@ public final class AppModel {
                 // await are reads of the store the composer is already diffing, which is why they are
                 // wired here rather than reached for: the engine holds the *policy* (when to wait, how
                 // long), the session supplies the two facts (`GitAutoCommitter.awaitCoveringSnapshot`).
+                //
+                // The generation the gate counts is `landedReloads` — completed *walks* rather than
+                // applied snapshots — because a value-equal reload skips the assignment and its
+                // counter since 2026-07-31, and a walk covers a flush's paths whether or not it found
+                // anything to change (`BoardStore.landedReloads`).
                 committer.awaitReloadQuiescence = { [weak store] in await store?.awaitQuiescence() }
-                committer.snapshotGeneration = { [weak store] in store?.snapshotGeneration }
+                committer.landedReloads = { [weak store] in store?.landedReloads }
                 // 02-architecture.md ▸ Write-failure surfacing, through the strip the board window
                 // already renders: a genuine commit failure means "your edits are saved, history has
                 // stopped advancing", which is exactly what the standing suspension row says. Lock