feat(tabs): search sessions by name on the vertical rail

A "Search sessions" box at the top of the vertical tab rail narrows the
list to the tabs whose name matches (case-insensitive substring; a web
tab matches by its title). It searches every group, collapsed ones
included: while a search runs the projection draws every group open and
the header will not toggle, and the stored per-device collapse state is
left alone. Groups with no match hide, an empty result says "No sessions
match", and the flat rail (no groups) filters the same way. Escape or
the clear button empties it; leaving the vertical orientation resets it.

It is a view filter only: rows get the same tab-filtered-out class the
sidebar filter box uses, through one shared _applyTabListFilter() over
the pure CodemanTabSearch matcher in constants.js. Grouping, order,
Alt+N badges and drag are untouched, nothing is persisted or sent to
the server. The sidebar keeps matching name plus working directory.

In the grouped tree, hidden rows and the headers of emptied groups leave
the roving walk and posinset/setsize, and the tab stop moves onto a
visible item. zh-CN strings added.

CLAUDE.md

@@ -333,7 +333,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **Mobile tab strip scrolling** (issue #257): under 768px the tab strip scrolls horizontally, so the active tab must be kept reachable. `_updateActiveTabImmediate()` reveals it via `computeTabScrollLeft()` (constants.js, rect math on the strip's own `scrollLeft`, never `scrollIntoView()`, which scrolls the document under the fixed header); `_fullRenderSessionTabs()` must restore `scrollLeft` across rebuilds and re-reveal only when the active tab changed (`_lastRenderedActiveTabId`) or, grouped by state, the ACTIVE tab moved to another state band (`_noteActiveTabBand()`, both render paths, scrolling row only; another tab's move never scrolls). ⚠️ The phone-block `min-width` on `.session-tab.active .tab-name` keeps the tab's centre off the gear/close icons, sized for numberless tabs 10+ (floor 40px); do not shrink it. ⚠️ Never reintroduce hoisting the active session to the front of the strip. Tests: `test/mobile-tab-tap-zones.test.ts`, `test/tab-triage.test.ts`. → [architecture-invariants#mobile-tab-strip-scrolling](docs/architecture-invariants.md#mobile-tab-strip-scrolling)
 
-**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)
+**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. ⚠️ The rail's **Search sessions** box (`setTabRailSearch`, in memory only) and the sidebar filter share ONE row filter, `_applyTabListFilter()` over the pure `CodemanTabSearch` (constants.js): classes only, never a reorder or layout write; the rail matches the name, the sidebar name + folder. While it runs `_projectTabGroups()` projects every group open (a collapsed group's rows are not in the DOM) and `toggleTabGroupCollapsed()` refuses, leaving the stored collapse untouched; `applyTabOrientation()` clears it off the rail. Tests: `test/tab-rail-search.test.ts`, `test/tab-rail-search.browser.test.ts`. → [architecture-invariants#session-list-layout-header-strip-vs-left-sidebar](docs/architecture-invariants.md#session-list-layout-header-strip-vs-left-sidebar)
 
 **Tab layouts** (`tabArrangement`, per-device, default `classic`; `state`/`case`/`ledger` are opt-in; Discussion #426): `state` (option C) splits the list into needs you / waiting / working / idle (idle is `quiet`: its heading stays as the row's anchor but draws no label; `tabStateOrder: 'urgent-last'` flips the order, needs you at the bottom): rows in the desktop header strip with left-aligned labels in a measured column (the brand sits over the strip's corner, so the rows after the first start under "Codeman"), sections in the flat rail and the sidebar, inline dividers on the tablet strip, group order with no headings on phones. `case` (option A) wraps each case's tabs in one `.tab-cluster` box and hides the `-<case>` of a generated name (`.tab-name-case`). `ledger` (option B) is a CSS-only grid on the desktop header strip. `classic` is the old strip. Pure cores: `CodemanTabTriage` and `CodemanTabClusters` (constants.js). ⚠️ `state` is the flex `order` property plus `aria-hidden` heading/break elements reconciled in place by `_syncTabTriageChrome()` after BOTH render paths, never a DOM reorder (a state change is an incremental pass). ⚠️ `case` boxes ARE a DOM grouping, so the incremental path rebuilds whenever `_tabClusterLayout().key` changes; membership follows `_mobileOverviewCaseFor()` like the home screens. ⚠️ Drag only reorders within a group or box (`_isTabDropAcrossGroups()`). ⚠️ Named groups in the vertical rail win over both groupings. ⚠️ `classic` must leave no trace (no headings, no inline order, no boxes, no name split), and the ledger must not change the markup. Tests: `test/tab-triage.test.ts`, `test/tab-clusters.test.ts`. → [architecture-invariants#tab-layouts-by-state-by-case-ledger](docs/architecture-invariants.md#tab-layouts-by-state-by-case-ledger)