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/BoardDecisionSurfaceTests.swift

@@ -719,7 +719,7 @@ struct BoardDecisionSurfaceRepairCommitTests {
 
         // The repository, with everything as it stands committed — including the broken root, which is
         // what makes the repair a real change rather than a fresh file.
-        let git = try #require(HistoryStore.compose(boardRoot: fixture.root, tier: .pro, ledger: EchoLedger()))
+        let git = HistoryStore.compose(boardRoot: fixture.root, ledger: EchoLedger())
         #expect(await git.addGit())
         let commitsBefore = try repairHistory(at: fixture.root).count
         git.stopAutoCommit()