feat: sort both home-screen session lists by activity, not tab order

The phone overview and the desktop tab rail list the same sessions, so
they now share one order (CodemanSessionOrder in constants.js, pure and
unit-tested): blocked on you first (longest-blocked at the top), then
running longest-turn-first, then quiet most-recently-quiet first.

The tiebreak flips direction halfway down on purpose: for a state a
session is still in, longer is more urgent; for a state it has stopped
in, more recent is more relevant. The running group keys off the pane's
last Enter (lastSubmitAt), never lastActivityAt, because a working pane
repaints about once a second and would rank every turn as freshly
started. A 0 stamp means "unknown" and sorts last within its state.

The desktop rail was previously in raw tab order. Its number badge stays
the Alt+1..9 index, so on a sorted rail it deliberately no longer runs
1,2,3 downward: it names a shortcut, not a row position. Its second
stamp changes from "active 3m ago" to the state duration the order is
computed from ("created 1d ago . working 40m"), since both working rows
otherwise read "active just now" and the order looked arbitrary.

The tab strip itself is untouched: still user-ordered and drag-sortable.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/web/public/mobile-overview.js

@@ -8,6 +8,10 @@
  * errored sessions), then SPACES (cases, expandable to their sessions), then
  * WORKING and IDLE / DONE.
  *
+ * Rows inside a section are ordered by `CodemanSessionOrder` (constants.js),
+ * the SAME comparator the desktop rail uses: blocked longest-first, then
+ * running longest-first, then quiet most-recently-quiet first.
+ *
  * PHONE ONLY. The gate is `shouldUseMobileOverview()` (viewport < 430px, not a
  * popped-out solo window, per-device setting on). Tablet and desktop keep the
  * welcome overlay untouched. The container ships with the `hidden` attribute and
@@ -25,6 +29,7 @@
  * `buildMobileOverviewModel()` is pure and unit-tested (test/mobile-overview.test.ts).
  *
  * @mixin Extends CodemanApp.prototype via Object.assign
+ * @dependency constants.js (CodemanSessionOrder, the shared row comparator)
  * @dependency app.js (this.sessions, this.cases, this.pendingHooks, selectSession, run)
  * @dependency ralph-panel.js (formatRelativeTime, the app's one relative-time formatter)
  * @dependency mobile-handlers.js (MobileDetection)
@@ -35,16 +40,6 @@
 /** Viewport width that counts as a phone. Matches the mobile.css phone block. */
 const MOBILE_OVERVIEW_PHONE_QUERY = '(max-width: 430px)';
 
-/** Sort rank per state: the most demanding thing sorts first inside a section. */
-const MOBILE_OVERVIEW_STATE_RANK = {
-  needs: 0,
-  error: 1,
-  waiting: 2,
-  working: 3,
-  idle: 4,
-  done: 5,
-};
-
 /** How many past conversations show before the "Show all" toggle. */
 const MOBILE_OVERVIEW_PAST_LIMIT = 8;
 
@@ -188,17 +183,19 @@ Object.assign(CodemanApp.prototype, {
         // Epoch ms, straight off the session payload; formatting happens at
         // render time so the clock can redo it without a re-render.
         createdAt: Number(session.createdAt) || 0,
+        // Raw stamps for the shared order comparator; `since` above is the same
+        // pair resolved for DISPLAY, and the two must not drift apart.
+        lastActivityAt: Number(session.lastActivityAt) || 0,
+        lastSubmitAt: Number(session.lastSubmitAt) || 0,
         since: this._mobileOverviewSince(state, session),
         orderIndex: orderIndex === -1 ? Number.MAX_SAFE_INTEGER : orderIndex,
       };
     });
 
-    const bySeverityThenOrder = (a, b) => {
-      const rank = MOBILE_OVERVIEW_STATE_RANK[a.state] - MOBILE_OVERVIEW_STATE_RANK[b.state];
-      return rank !== 0 ? rank : a.orderIndex - b.orderIndex;
-    };
-
-    const inSection = (states) => rows.filter((r) => states.includes(r.state)).sort(bySeverityThenOrder);
+    // Order is `CodemanSessionOrder` (constants.js), shared with the desktop
+    // rail: blocked first (longest-blocked at the top), then running
+    // longest-first, then quiet most-recent-first.
+    const inSection = (states) => window.CodemanSessionOrder.sort(rows.filter((r) => states.includes(r.state)));
 
     // Past = conversations from the unified list that are not currently live.
     // The endpoint already folds a transcript into its owning session (via the