refactor(home): let useSessionManagement own six session states

5.4: sessionsCursor / showArchivedSessions / sessionMenuId /
pendingSessionDeletion / sessionDetailLoadingId / sessionFullPrompt move into
use-session-management.ts, which now also computes visibleSessions from the
archived flag it owns. Home reads back only what its own JSX renders.

sessions / activeSessionId / creatingSession / pendingSessionId stay in the
shell: each is read by the bootstrap effect or the consultation run before the
session hook is called. Reasons are listed one by one in the progress record.

useSessionManagement params 41 -> 34, useProfileOnboarding 38 -> 26.

The growth contract tightens to useState 36 / useRef 37 / lines 1846 and gains an
assertion that useSessionManagement still runs before useRectificationSurface,
with the opener handed over through rectificationSessionOpenerRef.

Zero behavior change, zero copy change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JUei7K13cYxLHE3Axe4A45

frontend/tests/home-shell-growth-contract.test.ts

@@ -4,16 +4,19 @@ import test from "node:test";
 
 const pageSource = readFileSync(new URL("../src/app/page.tsx", import.meta.url), "utf8");
 
-// Measured 2026-09-16 after home-state-lowering on origin/staging @ 3b17c1b2.
-// Line count: (pageSource.match(/\n/g) ?? []).length, same as `wc -l` = 1931.
+// Measured 2026-09-16 after home-state-lowering batch 2 on origin/staging @ 37e6c519.
+// Line count: (pageSource.match(/\n/g) ?? []).length, same as `wc -l` = 1846.
 // Hook counts use \buseState[<(] / \buseRef[<(] so `useState<Type>(` is not missed.
-// Former caps were useState 66 / useRef 41 / lines 1951 on freeze-metric @ 51a65d92.
-// This round moved 14 rectification useStates out of Home (15 → 1 shell object)
-// and 2 rectification refs into useRectificationSurface.
-const PAGE_LINE_COUNT_BASELINE = 1931;
+// Former caps were useState 52 / useRef 39 / lines 1931 after batch 1 @ f8e607c2,
+// and useState 66 / useRef 41 / lines 1951 on freeze-metric @ 51a65d92.
+// Batch 2 moved 4 synastry useStates into useSynastry, 6 profile useStates into
+// useProfileOnboarding and 6 session useStates into useSessionManagement, and
+// dropped the two guided-birth-time callback refs that the profile hook no longer
+// needs now that it runs before useBirthTimeGuidedJourney.
+const PAGE_LINE_COUNT_BASELINE = 1846;
 const PAGE_LINE_COUNT_CAP = PAGE_LINE_COUNT_BASELINE + 150;
-const HOME_USE_STATE_CAP = 52;
-const HOME_USE_REF_CAP = 39;
+const HOME_USE_STATE_CAP = 36;
+const HOME_USE_REF_CAP = 37;
 
 const USE_STATE_RE = /\buseState[<(]/g;
 const USE_REF_RE = /\buseRef[<(]/g;
@@ -52,3 +55,29 @@ test("page.tsx line count stays within the coarse guardrail", () => {
     `page.tsx has ${n} lines; cap is ${PAGE_LINE_COUNT_CAP} (${PAGE_LINE_COUNT_BASELINE} baseline + 150).`,
   );
 });
+
+test("useSessionManagement still runs before useRectificationSurface", () => {
+  // Batch 1 established the order: useSessionManagement needs an opener for
+  // history rectification sessions, and useRectificationSurface is what supplies
+  // it, so the opener is handed over through rectificationSessionOpenerRef
+  // instead of by calling the surface hook first. Batch 2 moved hook calls
+  // around; this pins the constraint so a later reorder cannot silently break
+  // opening a rectification session from the sidebar.
+  const home = homeSource(pageSource);
+  const sessionCall = home.indexOf("= useSessionManagement({");
+  const surfaceCall = home.indexOf("= useRectificationSurface({");
+  const openerRef = home.indexOf("const rectificationSessionOpenerRef = useRef(");
+  assert.notEqual(sessionCall, -1, "Home must call useSessionManagement");
+  assert.notEqual(surfaceCall, -1, "Home must call useRectificationSurface");
+  assert.notEqual(openerRef, -1, "Home must declare rectificationSessionOpenerRef");
+  assert.ok(openerRef < sessionCall, "the opener ref must exist before useSessionManagement reads it");
+  assert.ok(
+    sessionCall < surfaceCall,
+    "useSessionManagement must run before useRectificationSurface; it receives the opener through rectificationSessionOpenerRef",
+  );
+  assert.match(
+    home.slice(sessionCall, surfaceCall),
+    /openRectificationSession: \(exactSessionId\) => rectificationSessionOpenerRef\.current\(exactSessionId\)/,
+  );
+  assert.match(home.slice(surfaceCall), /rectificationSessionOpenerRef,/);
+});