feat(sidebar): add a rich session sidebar that carries the home screen's row detail

Session List Layout gains a third option. The old "Left sidebar" becomes
"Left sidebar simple" and is unchanged down to the byte; the new "Left sidebar"
puts on each row what the desktop home rail and the phone overview already show:
when the session was first created, how long it has been in the state it is in,
and a status pill naming that state.

A docked column is not a tab strip. It has width to spare and a row per session
either way, and "name + folder" is the whole story a TAB can tell, not the whole
story there is. This is the information that was missing, and it already existed
one surface over.

Both sidebar values are the same layout, and both set data-session-list="sidebar";
the row detail rides on a separate data-sidebar-detail attribute. That split is
the load-bearing decision here: every one of the ~25 isSessionSidebarActive()
call sites and every html[data-session-list="sidebar"] rule in styles.css and
mobile.css keeps matching both variants without being touched. A third
data-session-list value would have meant auditing and editing all of them.

- Stored values: 'header', 'sidebar' (simple), 'sidebar-rich'. Anyone already on
  'sidebar' keeps exactly the layout they picked — the rename is label-only.
- State classification and the "how long has it been like this" anchor come from
  _mobileOverviewState() / _mobileOverviewSince(), not re-derived, so the three
  surfaces cannot disagree about what "working" means. A working pane repaints
  ~1/s, so its duration is measured from the turn's last Enter: a running turn
  reads "working 12m", not "0m".
- Stamps refresh in place on a 20s clock rather than by re-rendering — a rebuild
  would restart every load spinner and alert animation in the list, twice a
  minute. The clock runs only while rich rows are on screen, and is stopped from
  both render paths and from applySessionListLayout().
- The incremental render path updates the pill, the accent class and the since
  anchor; a tick alone cannot see a state change, and a new turn re-stamps
  lastSubmitAt without changing state.
- applySessionListLayout() now re-renders on a DETAIL change too. simple <-> rich
  leaves data-session-list on 'sidebar' both times, and the meta line is emitted
  by the row template rather than toggled by CSS, so the old layout-only test
  would have flipped the setting and repainted nothing.
- Width: 300px for the extra line. The collapsed 44px rail and the handheld
  drawer are both explicitly held back from it — the desktop rule is (0,3,1) and
  would otherwise out-specify mobile.css's (0,2,1) drawer base and pin a 320px
  phone's drawer to 300px.
- Missing/stale mobile-overview.js degrades to a row with no meta line rather
  than throwing and taking the whole tab strip down.

15 new tests cover the attribute split, the solo-window override, the
detail-change re-render, the row model, both render paths, the clock lifecycle
and the mobile width guard.

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

src/web/public/index.html

@@ -62,7 +62,7 @@
        app.js, NOT the handheld storage-key test `m`. Use a different predicate
        here and boot will contradict this value, animating the drawer open by
        itself on every load between 768 and 1023px. -->
-  <script>try{var m=window.innerWidth<768||(('ontouchstart' in window||navigator.maxTouchPoints>0)&&window.innerWidth<1024);var k=m?'codeman-app-settings-mobile':'codeman-app-settings';var L=JSON.parse(localStorage.getItem(k)||'{}').sessionListLayout;var solo=/^\/session\//.test(location.pathname);var C=localStorage.getItem('codeman-sidebar-collapsed');document.documentElement.dataset.sessionList=(L==='sidebar'&&!solo)?'sidebar':'header';document.documentElement.dataset.sidebar=(C===null?window.innerWidth<1024:C==='1')?'collapsed':'expanded';}catch(e){document.documentElement.dataset.sessionList='header';document.documentElement.dataset.sidebar='expanded';}</script>
+  <script>try{var m=window.innerWidth<768||(('ontouchstart' in window||navigator.maxTouchPoints>0)&&window.innerWidth<1024);var k=m?'codeman-app-settings-mobile':'codeman-app-settings';var L=JSON.parse(localStorage.getItem(k)||'{}').sessionListLayout;var solo=/^\/session\//.test(location.pathname);var C=localStorage.getItem('codeman-sidebar-collapsed');var S=(L==='sidebar'||L==='sidebar-rich')&&!solo;document.documentElement.dataset.sessionList=S?'sidebar':'header';document.documentElement.dataset.sidebarDetail=(S&&L==='sidebar-rich')?'rich':'simple';document.documentElement.dataset.sidebar=(C===null?window.innerWidth<1024:C==='1')?'collapsed':'expanded';}catch(e){document.documentElement.dataset.sessionList='header';document.documentElement.dataset.sidebarDetail='simple';document.documentElement.dataset.sidebar='expanded';}</script>
   <!-- Inline critical CSS for instant skeleton paint (before styles.css loads) -->
   <style>
     .loading-skeleton{display:flex;flex-direction:column;height:100vh;height:100dvh;background:var(--bg-dark,#11151c)}
@@ -1843,11 +1843,12 @@
                   <div class="set-row has-field" data-search="session list layout sidebar tab strip vertical">
                     <div class="set-row-text">
                       <span class="set-row-label">Session List Layout</span>
-                      <span class="set-row-desc">Horizontal strip in the header, or a collapsible left sidebar (Alt+B).</span>
+                      <span class="set-row-desc">Horizontal strip in the header, or a collapsible left sidebar (Alt+B). The rich sidebar carries the same per-session detail as the home screen.</span>
                     </div>
                     <select id="appSettingsSessionListLayout" class="set-select">
                       <option value="header">Header tab strip</option>
-                      <option value="sidebar">Left sidebar</option>
+                      <option value="sidebar">Left sidebar simple</option>
+                      <option value="sidebar-rich">Left sidebar</option>
                     </select>
                   </div>
                   <div class="set-row" data-search="tall tabs folder name two rows">