Make the card window the commit unit on Pro boards

Phase C of the two-level undo card: the committer stages around the
whole open card folder — comments included — so gestures in an open
window never land in interim commits; window close flushes the session
as one semantically-named commit ("Edit card 'X'" with the thread as
body bullets, "Mixed update — N changes to card 'X'" when events mix),
with the two-commit foreign/user split preserved and the
comments/.trash purge riding the same bracket. Comment gestures lose
their per-gesture commits structurally (they write inside the held
folder). Branch-switch settle releases every window's staging before
checkout and re-arms on resume.

Fixes two latent pro-m1 defects: the committer was composed without
the store's EchoLedger, so every production commit classified foreign
and was authored Lanework External; and interim flushes dropped
harvest receipts they had not spent, unvouching the session's own
writes at close. Also lands 06's mixed-subject re-ruling (the retired
"Update board" fallback) and phase B's two files missed by the
previous commit's pathspec.

2444 tests in 422 suites green.

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

Kanban/UI/Card/CardBodyEditSession.swift

@@ -113,16 +113,17 @@ public final class CardBodyEditSession {
     /// **The session boundary, announced** — called with `true` when an Edit session opens and
     /// `false` when it ends, and with nothing in between.
     ///
-    /// `CardWindowHost` points it at the board's auto-committer, which registers the card's folder to
-    /// stage around while the session stands and **nudges** when it ends (06-history-undo.md ▸ Rules
-    /// ▸ Auto-commit: the Edit→Preview flip is "the effective Save button", and raw-source entry and
-    /// window close end the session too). That nudge is what turns a session's several debounced
-    /// saves into exactly one commit: they commit nothing while the folder is excluded, and the
-    /// whole diff becomes committable at once when it is not.
+    /// **No longer the committer's stage-around boundary** (06-history-undo.md ▸ Rules ▸ Auto-commit,
+    /// widened 2026-07-31 — "Board history sees card-window sessions, not gestures"): the exclusion
+    /// used to open and close with this flip, and it now opens with the *window* and releases when its
+    /// session ends, so a comment posted with the body in Preview is inside the same one commit as the
+    /// body. `CardWindowHost` therefore no longer wires this to anything, and the Edit→Preview flip is
+    /// a save point rather than a commit point.
     ///
-    /// A closure for `save`'s reason exactly — this type is a buffer and a clock, and it stays
-    /// testable by having no idea what a repository is. `nil` (the free tier, a storeless test) means
-    /// nothing is listening, which is the same shape every other seam here takes.
+    /// The seam stays, unwired, because it is the only announcement of the boundary this type makes
+    /// and the ordering it carries — that the flush precedes the announcement — is a property worth
+    /// keeping proved (`AutoCommitTests`). A closure for `save`'s reason exactly: this type is a
+    /// buffer and a clock, and it stays testable by having no idea what a repository is.
     @ObservationIgnored
     public var editSessionDidChange: ((_ isEditing: Bool) -> Void)?