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/BranchSwitchTests.swift

@@ -37,7 +37,7 @@ private func makeBoard() throws -> WriterFixture {
 @MainActor
 private func makeGitBoard() async throws -> (fixture: WriterFixture, git: HistoryStore) {
     let fixture = try makeBoard()
-    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())
     await git.refreshBranch()
     return (fixture, git)
@@ -1034,7 +1034,7 @@ struct BoardGitBranchSurfaceTests {
     /// is that git mode now carries controls rather than a read-only line.
     @Test("Git mode still resolves to the branch section — now the one with controls in it")
     func gitModeResolvesToTheBranchSection() {
-        #expect(BoardGitSection.resolve(tier: .pro, mode: .git, hasGitDirectory: true) == .branch)
+        #expect(BoardGitSection.resolve(mode: .git) == .branch)
     }
 }