The tier axis comes out of the git stack — compose unconditional, postures mode-driven

HistoryStore.compose(boardRoot📒) returns non-optional and runs for
every session — the nil the gate produced was the only nil it ever had.
makeHistoryProvider is a one-axis decision: git-mode boards bind the git
provider, everything else native, in every tier; Session.tier stays
recorded, dormant. BoardGitSection shrinks to the four mode postures
(.absent and .proPointer die, BoardGitNote and the .git probe with them);
every board carries all three popover tabs (BoardInfoTab.available
retired); the titlebar branch shows on any git-mode board; the settings
sheet and card History section stop reading tier. InertGitTests is
repurposed as UntouchedGitTests — the file layer still never opens .git,
now load-bearing for mode-none boards. The accessibility audit reaches the
settings sheet at last: the fixture board hosts it in every tier, so the
free-fixture disabled-row test becomes an open-and-audit test.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/History/NativeHistoryProvider.swift

@@ -2,8 +2,10 @@ import Foundation
 
 // MARK: - NativeHistoryProvider
 
-/// The free tier's undo substrate: one stack per board session (13-native-undo.md) — **and the
-/// substrate of every open card window's stack, in either tier** (re-ruled 2026-07-31, the
+/// The undo substrate of every board without app-managed git: one stack per board session
+/// (13-native-undo.md, whose header lost its tier axis with the 2026-08-07 pivot — the substrate is
+/// the board's mode alone, and git is opt-in per board, so a board nobody opted in keeps this stack
+/// for good) — **and the substrate of every open card window's stack, on any board** (re-ruled 2026-07-31, the
 /// session-coarsening model): a window's fine-grained gestures are values-based inverses whatever the
 /// board's own substrate is, so `CardWindowUndo` holds one of these too. Nothing below knows which of
 /// the two it is; both need the same four-line grammar.