feat(tabs,header): group tabs by state and add header stats styles (#426)

Two directions from Discussion #426, each a per-device setting and the
new default.

Tab Grouping (tabGrouping: 'state' | 'none', default 'state', option C):
tabs are grouped needs you (red, plus failed sessions), waiting (yellow),
working and idle (also ended, exited panes and web tabs), most urgent on
top. The desktop header strip draws a row per group with its label and
count in a left gutter; the flat vertical rail and the sidebar draw a
section per group; tablets keep their scrolling row with inline dividers;
phones keep the chip row in group order without headings. Classification
is the home screens' own (_mobileOverviewState/_mobileOverviewExit), the
fold into four groups is pure in CodemanTabTriage (constants.js). It is
flex `order` plus aria-hidden heading/break elements reconciled in place
after both render paths, never a DOM reorder, so Alt+N, the keyboard walk
and drag keep reading tab order; a drop is refused across groups. Named
groups in the vertical rail take precedence.

Header Stats Style (headerStatsStyle: 'classic' | 'compact' | 'tiles',
default 'tiles', option G): tiles give WS, CPU, MEM and each plan window
a label-over-value tile with a bar underneath; compact is one WS/CPU/MEM
pill with sparklines plus a plan-ring pill; classic is the header as
before. Desktop only (classic below 768px and in solo windows). The
clustered styles move #connectionIndicator into #headerSystemStats and
#planUsageChip after it, and classic moves them back to comment anchors;
WS stays out of a hidden System Stats pill. The extra parts are always
rendered and hidden by default in CSS, so classic is unchanged.

Tests: test/tab-triage.test.ts, test/header-stats-style.test.ts; three
source pins in test/tab-rail-order.test.ts follow renamed lines.

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

docs/wiki/Settings-Reference.md

@@ -62,6 +62,9 @@ Project Insights, File Browser, Subagents, Approvals Inbox, Read My Mind, Ultrac
 Ultracode Windows, Cron.
 
 Most default to off. The stock desktop header is system stats, File Viewer, and the gear.
+**Header Stats Style** picks how the system stats and plan usage are drawn: *Tiles*
+(default; label over value with a bar underneath), *Compact* (one pill with sparklines plus
+plan-usage rings) or *As before* (the bars and the `5H · 7D` chip). Desktop only, per device.
 New header controls never appear on phones. Split is desktop-only regardless of this
 setting — the button and the feature both stay off below a ~1180px viewport, where two
 resizable panes plus their divider have nowhere to go.
@@ -79,7 +82,8 @@ every session or only the active tab.
 | Interface Language     | English or Simplified Chinese. Per device.                                                 |
 | Session List Layout    | Header tab strip (default), a collapsible left sidebar, or the sidebar with detailed rows. See [The Dashboard](The-Dashboard#session-list-layout). |
 | Tab Orientation        | Keeps the header list but turns the strip vertical beside the terminal, resizable, with detailed rows by default. Desktop and tablet only. |
-| Vertical Rail Order    | *By activity* (default) sorts the rail the way the home screens are sorted; *Manual* keeps your tab order and drag-reordering. |
+| Tab Grouping           | *By state* (default) splits the tabs into needs you, waiting, working and idle: rows in the header, sections in the rail and sidebar. *None* keeps one list in tab order. See [The Dashboard](The-Dashboard#tab-grouping-by-state). |
+| Vertical Rail Order    | *By activity* (default) sorts the rail the way the home screens are sorted; *Manual* keeps your tab order and drag-reordering. With grouping by state it orders the rows inside each section. |
 | Tall Tabs              | Taller tab strip.                                                                          |
 | Pop-out Button on Tabs | Adds the detach control to tabs, with a per-tab override.                                  |
 | Spawn Lineage Lines    | Arcs from a parent tab to sessions it spawned. Desktop only, on by default.                |