fix: apply the review items for #682 at merge

docs: architecture-invariants (arrow-key walk section) names the phone swipe beside the arrow keys as following the drawn order
docs: root CLAUDE.md (Owner tab layouts) carves the phone swipe out of "every other order consumer reads sessionOrder"
test: pin the grouped-tree branch of _stripSessionOrder() (sorted rail, header and web tab skipped, groups not interleaved)
test: the step-in case uses a drawn order (homelab, w1, w2) that master's canonical walk and the old arithmetic cannot satisfy

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -895,7 +895,7 @@ Tests: `test/tab-rail-search.test.ts` (gate) and `test/tab-rail-search.browser.t
 
 ⚠️ **Row ORDER is a third rail attribute** (`tabRailSort: 'activity'|'manual'`, `data-tab-rail-sort`, default **activity**): a sorted rail answers the home screens' question with the home screens' answer, `CodemanSessionOrder` over rows classified by `_mobileOverviewState` (`_tabRailSortOrder` in app.js). ⚠️ **It is applied as the flex `order` property, never by reordering the DOM**: `#sessionTabs` stays in `sessionOrder`, so the Alt+N badge (`_tabIdx`, which therefore does NOT run 1,2,3 down a sorted rail — it names a shortcut, not a position), drag-and-drop, the arrow-key walk, the sidebar filter and `_scrollActiveTabIntoView()` all keep reading the list they always read, and a session changing state moves ONE inline style instead of forcing the full rebuild that would restart every card's animation on every SSE tick. The incremental render path therefore has to re-apply it (a state flip adds no tab, so the full rebuild is never reached) and an empty string is what clears it when sorting stops. ⚠️ Web tabs are pinned past the cards by a CSS `order: 9999` rather than an inline one, since `renderWebviewTabs()` emits the same markup for every layout; the flex default of 0 would interleave them among the sorted sessions. ⚠️ `setupTabDragHandlers()` sets `draggable="false"` and returns while sorting is on: the drop rewrites `sessionOrder` correctly and the sort then puts the card straight back, so the affordance would be a lie — `'manual'` is the way back to drag-reordering.
 
-⚠️ **The arrow-key walk is the one place that must follow the SORT rather than the DOM**: `_tabKeydownHandler` steps `querySelectorAll` order, which is `sessionOrder`, so on a sorted rail ArrowDown from the top card landed wherever that session sat in the tab order instead of on the card below it. It now sorts its node list by the COMPUTED `order` first (computed, not inline: web tabs get their `order: 9999` from CSS and would otherwise read as 0 and lead the walk). This is the exception that proves the DOM-stays-in-sessionOrder rule: the badge, drag model and Alt+N index all deliberately keep reading the DOM, and only the thing the user steps with their eyes follows the paint.
+⚠️ **The arrow-key walk and the phone swipe are the two places that must follow the SORT rather than the DOM**: `_tabKeydownHandler` steps `querySelectorAll` order, which is `sessionOrder`, so on a sorted rail ArrowDown from the top card landed wherever that session sat in the tab order instead of on the card below it. It now sorts its node list by the COMPUTED `order` first (computed, not inline: web tabs get their `order: 9999` from CSS and would otherwise read as 0 and lead the walk). That walk is `_visibleTabRows()`, and the phone swipe shares it: `SwipeHandler` calls `nextSession({ visual: true })` / `prevSession({ visual: true })`, which step through `_stripSessionOrder()` (the grouped tree's session rows via `_tabTreeItems()`, otherwise `_visibleTabRows()`, web tabs skipped), so a swipe lands on the tab drawn next to the current one in the case and state layouts, a sorted rail and named groups; Alt+[ / Alt+], Ctrl+Tab and Alt+1..9 keep `sessionOrder`. An active session the list does not draw steps in at the first row (next) or the last (previous), and an empty drawn list goes nowhere rather than falling back to a hidden session (`test/session-swipe-gesture.test.ts`). This is the exception that proves the DOM-stays-in-sessionOrder rule: the badge, drag model and Alt+N index all deliberately keep reading the DOM, and only the things the user steps with their eyes (the arrow keys and the swipe) follow the paint.
 
 ### Split-pane sessions