feat(tabs): no label on the idle row (#426)

Idle is the default state of a tab, so naming it only adds noise. The
idle group is now quiet: its heading element stays (it anchors the row's
order band and, as the first row, holds its place beside the brand) but
draws no label or count. Needs you, Waiting and Working are unchanged.

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

docs/architecture-invariants.md

@@ -871,7 +871,7 @@ Tests: `test/terminal-touch-tap.test.ts`.
 
 **Tab layouts** (`tabArrangement`, per-device, default `state`; Discussion #426): App Settings → Appearance → Tabs → **Tab Layout**. Four values: `state` (option C), `case` (option A), `ledger` (option B) and `classic`, the strip as before. `<html data-tab-arrangement>` is stamped pre-paint and by `applyTabOrientation()`; the render paths read it through `isTabTriage()`, `isTabClusters()` and `isTabLedger()`. Named groups in the vertical rail (owner tab layouts, `_projectTabGroups()` non-null) win over both groupings, and the grouped tree renders as before.
 
-**By state.** The list is split into four groups: **needs you** (a permission or question dialog; a failed session joins it), **waiting** (idle prompt pending), **working**, **idle** (also ended sessions, an agent that exited inside a live pane, and web tabs). `tabStateOrder` (`urgent-first` default, `urgent-last`) decides which end they start from; only the group order flips, never the rows inside a group. The desktop header strip draws a row per group with its label left-aligned in a column that `_sizeTabTriageGutter()` measures to the widest label on screen (re-measured only when the label text changes, and once on `document.fonts.ready`), so no row carries a fixed gutter's worth of empty space. The brand leaves the flow and sits over the strip's top-left corner (`.header:has(...)`), so the first row's heading (`.tab-triage-head--lead`, natural width) is pushed past it by `--tab-triage-brand` (a ResizeObserver keeps that width, so no render pass reads layout for it) and every later row starts at the edge, under "Codeman"; the flat rail and the sidebar draw a section per group; the tablet strip (600-767px) keeps its scrolling row with the headings as inline dividers; phones keep their chip row in group order with the headings hidden (mobile.css). Classification is `_mobileOverviewState()` + `_mobileOverviewExit()`, the home screens' own; the fold into four groups and the order bands are pure in `CodemanTabTriage` (constants.js, `computeTabTriageLayout()`).
+**By state.** The list is split into four groups: **needs you** (a permission or question dialog; a failed session joins it), **waiting** (idle prompt pending), **working**, **idle** (also ended sessions, an agent that exited inside a live pane, and web tabs). Idle is `quiet` (`TAB_TRIAGE_GROUPS`): its heading element still exists, because it anchors the row's `order` band and, as the lead, holds the row's place beside the brand, but it draws no label or count (`.tab-triage-head--quiet`). `tabStateOrder` (`urgent-first` default, `urgent-last`) decides which end they start from; only the group order flips, never the rows inside a group. The desktop header strip draws a row per group with its label left-aligned in a column that `_sizeTabTriageGutter()` measures to the widest label on screen (re-measured only when the label text changes, and once on `document.fonts.ready`), so no row carries a fixed gutter's worth of empty space. The brand leaves the flow and sits over the strip's top-left corner (`.header:has(...)`), so the first row's heading (`.tab-triage-head--lead`, natural width) is pushed past it by `--tab-triage-brand` (a ResizeObserver keeps that width, so no render pass reads layout for it) and every later row starts at the edge, under "Codeman"; the flat rail and the sidebar draw a section per group; the tablet strip (600-767px) keeps its scrolling row with the headings as inline dividers; phones keep their chip row in group order with the headings hidden (mobile.css). Classification is `_mobileOverviewState()` + `_mobileOverviewExit()`, the home screens' own; the fold into four groups and the order bands are pure in `CodemanTabTriage` (constants.js, `computeTabTriageLayout()`).
 
 ⚠️ **By state is the flex `order` property, never a DOM reorder**, exactly like the sorted rail: `#sessionTabs` stays in `sessionOrder`, so the Alt+N badges, drag, the keyboard walk (which sorts by COMPUTED order) and the sidebar filter keep reading the list they always read. Each group owns a band of `TAB_TRIAGE_STRIDE` order values: its heading, its rows, its web tabs, then the row break that ends the header line. The headings and breaks are `aria-hidden` direct children of `#sessionTabs`, reconciled in place by `_syncTabTriageChrome()` after BOTH render paths, because a state change is an incremental pass and can still empty a group or fill a new one. Inside a header row tabs keep TAB order; a sorted rail ranks each section the way it ranks the flat rail. The header strip only wraps into rows on desktop, where `updateTabOverflowMode()` forces `tabs-auto-wrap`; the breaks only display in a wrapping strip, since a `flex-basis: 100%` break in a nowrap scroller would steal width.
 

docs/wiki/The-Dashboard.md

@@ -55,8 +55,9 @@ per device, so a sidebar on your desktop does not force one onto your phone.
 | **Working**   | A turn is running.                                                                  |
 | **Idle**      | Everything quiet, including ended sessions, agents that exited inside their pane, and web tabs. |
 
-In the header each group is a row with its name and count on the left; a group with more
-tabs than fit on one line continues under its own tabs. **State Order → Needs you at the
+In the header each group is a row with its name and count on the left (Idle, the quiet
+default, carries no label); a group with more tabs than fit on one line continues on the
+next line. **State Order → Needs you at the
 bottom** turns the rows the other way up, so the needs-you row sits right above the
 terminal. Empty groups are not shown. These are the same states the phone overview and the
 desktop home rail use, and tabs move between groups on their own as their state changes.