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

KanbanTests/CardSessionCommitTests.swift

@@ -137,7 +137,7 @@ private func makeWindow() async throws -> Window {
     let store = try BoardStore(rootURL: fixture.root)
     await store.awaitQuiescence()
 
-    let git = try #require(HistoryStore.compose(boardRoot: fixture.root, tier: .pro, ledger: store.echoes))
+    let git = HistoryStore.compose(boardRoot: fixture.root, ledger: store.echoes)
     #expect(await git.addGit())
 
     let committer = try #require(git.committer)
@@ -494,7 +494,7 @@ struct CardSessionStagingWiringTests {
         try fixture.item("", Item.board)
         try fixture.item(Ident.lane1, Item.rich(order: "1024", title: "Todo"))
         try fixture.item(cardPath, Item.rich(order: "1024", title: "Fix login"))
-        let seed = try #require(HistoryStore.compose(boardRoot: fixture.root, tier: .pro))
+        let seed = HistoryStore.compose(boardRoot: fixture.root)
         #expect(await seed.addGit())
         return (fixture, try openBoard(model, at: fixture.root))
     }