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>

CLAUDE.md

@@ -330,6 +330,10 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **Session list layout: header strip or left sidebar** (`sessionListLayout`, default `header`; per-device via `displayKeys`, also in `SettingsUpdateSchema`): the list can move into a collapsible `<aside>` (Alt+B, `toggleSessionSidebar`) or, via `tabOrientation`, a resizable vertical `#tabRail` (desktop/tablet only). ⚠️ There is ONE `#sessionTabs`, MOVED between hosts, never a second list: `applySessionListLayout()` runs first, then `applyTabOrientation()`, both BEFORE `applyTabWrapSettings()`, and both arm/disarm `_startSidebarRichClock()`. ⚠️ Axis decisions use `_isVerticalTabList()`, never `isSessionSidebarActive()` alone. ⚠️ Rich rows share one gate, `isRichTabRows()`; rich CSS pairs sidebar+rail with comma-grouped selectors, never `:is()`, and card rules stay rail-scoped. ⚠️ Rail sort (`tabRailSort`, default `activity`) is the flex `order` property only, never a DOM reorder; the arrow-key walk alone follows computed `order`. ⚠️ Leaving sidebar mode clears `_sidebarFilter`; the handheld overlay drawer is `inert` when closed, the docked rail never. → [architecture-invariants#session-list-layout-header-strip-vs-left-sidebar](docs/architecture-invariants.md#session-list-layout-header-strip-vs-left-sidebar)
 
+**Tab grouping by state** (`tabGrouping`, per-device, default `state`; Discussion #426 option C): the tab list splits into needs you / waiting / working / idle, most urgent on top: rows in the desktop header strip, sections in the flat rail and the sidebar, inline dividers on the tablet strip, group order with no headings on phones. Classification is `_mobileOverviewState()` + `_mobileOverviewExit()`; the fold and the order bands are pure in `CodemanTabTriage` (constants.js). ⚠️ It is the flex `order` property plus `aria-hidden` heading/break elements reconciled in place by `_syncTabTriageChrome()` after BOTH render paths, never a DOM reorder (Alt+N, drag and the keyboard walk keep reading tab order). ⚠️ Drag only reorders within a group (`_isTabDropAcrossTriageGroups()`). ⚠️ Named groups in the vertical rail win: triage is off whenever `_projectTabGroups()` is non-null. ⚠️ `'none'` must leave no trace (no headings, no inline order, no `tabs-triage` class). Tests: `test/tab-triage.test.ts`. → [architecture-invariants#tab-grouping-by-state](docs/architecture-invariants.md#tab-grouping-by-state)
+
+**Header stats styles** (`headerStatsStyle`, per-device, desktop only, default `tiles`; Discussion #426 option G): `tiles` / `compact` (pill + sparklines + plan rings) / `classic` (as before), keyed on `data-header-stats` (pre-paint + `applyHeaderStatsStyle()`), forced to `classic` below 768px and in a solo window. ⚠️ The clustered styles MOVE `#connectionIndicator` into `#headerSystemStats` and `#planUsageChip` right after it; `classic` moves them back to comment anchors. ⚠️ WS joins the pill only while System Stats is shown. ⚠️ The extra parts (sparklines, tile words, rings, meters) are always rendered and hidden by default in CSS, which is what keeps `classic` unchanged; tile words are derived beside the connection descriptor, never added to it (`test/connection-indicator.test.ts` pins its shape). Tests: `test/header-stats-style.test.ts`. → [architecture-invariants#header-stats-styles](docs/architecture-invariants.md#header-stats-styles)
+
 **Phone overview home screen** (`mobile-overview.js`, per-device `mobileOverviewEnabled`, default ON): under 600px the "C" logo shows NEEDS YOU / CURRENT / PAST SESSIONS instead of the welcome overlay, branched in `showWelcome()`/`hideWelcome()` via width-driven `shouldUseMobileOverview()`. ⚠️ The container ships `hidden` and only this module removes it: never give `.mobile-overview` a bare `display` rule (desktop does not load `mobile.css`). ⚠️ The split Run button must carry the toolbar's own classes (`btn-toolbar btn-run mode-<backend>` / `btn-run-gear`) and mobile.css must set no `background`/`color` on it; row status must mirror the session-tab alert language. PAST rows resume through the shared `resumeHistorySession()`. Status pills carry `data-i18n-skip`. → [architecture-invariants#phone-overview-home-screen](docs/architecture-invariants.md#phone-overview-home-screen)
 
 **Desktop home tab rail** (`home-sessions.js`, desktop only): the welcome overlay's left gutter carries the open tabs as a rail docked flush left, full height, in overview order, each row showing `created … · <state> <duration>` from `_mobileOverviewSince()`; state classification is reused from mobile-overview.js (so it loads after it). ⚠️ The number badge is the Alt+1..9 tab-strip index, never renumber it to row position. ⚠️ The width gate lives in two places that must stay equal: `HOME_SESSIONS_MIN_WIDTH` (1180) and a `max-width: 1179px` media query. ⚠️ `.home-sessions[hidden]` must re-assert `display: none`. ⚠️ Size all children in `em` off the one `clamp()` knob, never `rem`/px. Age stamps tick in place (`_tickHomeSessionsTimes()`), never by re-render. Test: `test/home-sessions.test.ts`. → [architecture-invariants#desktop-home-tab-rail](docs/architecture-invariants.md#desktop-home-tab-rail)