fix(tabs): a found tab still drops onto the tile grid during a rail search (#580)

183efacc turned drag off while the rail search narrows the list, as the
owner asked, by refusing the flat manual rail's dragstart. That also
refused a drag that never reorders anything: with the tile grid open, a
found tab dragged onto a tile or an empty cell set no draggedTabId, so
_acceptTabDrops() (tile-grid.js) saw nothing and the drop was lost. On
the PR head that drop replaced or swapped the tile. The owner's reason
covers the reorder only: a reorder drop is saved for every device,
relative to rows the search hides, while the tile grid is per-device and
lands beside nothing hidden.

dragstart is unconditional again. The rows refuse the reorder instead:
their dragover returns before preventDefault while _tabRailSearchActive()
(the browser shows no-drop and fires no drop there), and their drop
returns before touching sessionOrder, for anything above the row that
might let a drop through. `draggable` stays on, so a cleared search
reorders with the same rows. The grouped rail's pointer drag keeps its
refusal in _onTabLayoutPointerDown(): it has no drop target besides the
rail.

Test: during a search that leaves both rows showing, dragstart is not
cancelled and sets draggedTabId, dragover on another row is not
accepted, a drop there leaves sessionOrder alone and saves nothing, the
real _acceptTabDrops() binder accepts the drag on a tile and hands it
the id, and after clearing the same rows reorder. It fails on the
previous commit, without the dragover guard, and without the drop guard.
CLAUDE.md, the invariants, the Dashboard wiki row and the release
changeset now say reordering by drag is off and a tile drop still works.

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

docs/architecture-invariants.md

@@ -802,7 +802,7 @@ Further detail: with many sessions the horizontal strip stops being scannable, w
 - **Collapsed groups.** A collapsed group's rows are not in the DOM, so a class cannot reveal them: the projection opens every group while the rail search runs (see Owner tab layouts), and `setTabRailSearch()` re-renders only when that changes the structure (`_isTabGroupStructureStale()`); every other keystroke only re-applies classes.
 - **Connectors.** Lineage lines and the subagent/ultracode connectors are anchored to row positions, and a keystroke re-renders nothing, so `_applyTabListFilter()` calls `updateConnectionLines()` whenever it actually showed or hid something (a row, a section, the state headings via `tabs-filtering`, the empty note). An unchanged re-apply at a render tail calls nothing, which keeps the incremental path's lineage gate meaningful. ⚠️ A hidden row still answers `getBoundingClientRect()` with an all-zero rect, which is truthy, so every floating window that anchors to its parent tab (the subagent and ultracode connectors' shared `tab:<id>` cache, both spawn positions, the ultracode genie) finds it through `_paintedSessionTab()` (app.js: the row only while `getClientRects()` is non-empty). An unpainted parent draws no connector, spawns where a window without a tab would, and tears down without the genie; otherwise all three started at the viewport's top-left corner. Lineage needs no guard, since `computeTree` drops zero-size rects.
 - **Escape.** The global key handler runs in the CAPTURE phase on `document`, before the box's inline `onkeydown`, so a `stopPropagation()` there comes too late: the global Escape branch claims an Escape whose target is `#tabRailSearch` while the box holds text (beside the group menu, the grouped-rail drag and the Tiles count menu) and routes it to `handleTabRailSearchKeydown()`. Without that, clearing the search also collapsed the Monitor and Subagents panels. An empty box leaves Escape to the global handler.
-- **No drag while searching** (owner decision): a drop is saved for every device, relative to rows the search hides. Both rail drags refuse in their start handlers (`_onTabLayoutPointerDown`, the flat rail's `dragstart`), never by flipping `draggable`, which only a render would restore.
+- **No reorder by drag while searching** (owner decision): a reorder drop is saved for every device (session order or the tab layout), relative to rows the search hides. The grouped rail's pointer drag does not start (`_onTabLayoutPointerDown`; it has no other drop target). The flat rail's ROWS refuse it instead: their `dragover` returns before `preventDefault` (the browser shows no-drop) and their `drop` returns before touching `sessionOrder`. Its `dragstart` and `draggable` stay on, because a found tab dragged onto the tile grid (`_acceptTabDrops`, which reads `draggedTabId`) is per-device and lands beside nothing the search hides, and because flipping `draggable` would need a render a keystroke never does.
 - **In memory only, cleared off the rail.** The text is never persisted or sent. `applyTabOrientation()` calls `_resetTabRailSearch()` before its render when the list leaves the vertical rail, the same reason leaving sidebar mode clears `_sidebarFilter`.
 
 Tests: `test/tab-rail-search.test.ts` (gate) and `test/tab-rail-search.browser.test.ts` (browser suite, not in the gate; it installs the real `setupEventListeners()` so the capture-before-inline Escape order is the shipped one).

docs/wiki/The-Dashboard.md

@@ -29,7 +29,7 @@ Session List Layout** can move it into a vertical sidebar on the left instead, a
 | -------------------- | --------------------------------------------------------------------------------- |
 | **Header tab strip** | The default. One list in tab order unless you pick another [Tab layout](#tab-layouts); it scrolls sideways on a phone. |
 | **Left sidebar**     | A vertical list with a filter box and a live session count. `Alt+B` collapses it to a narrow rail that keeps the status dots and task badges visible. On a phone it is an off-canvas drawer rather than a docked rail. A detailed variant adds the home screen's per-session line (`created 3d ago · working 12m`) and a status pill. |
-| **Vertical rail**    | The strip turned vertical beside the terminal, resizable, with detailed rows by default. **Vertical Rail Order** sorts it by activity (blocked on you first, then longest running, then most recently quiet), the same order as the home screens; pick *Manual* to get your own order and drag-reordering back. **Tab groups:** pick *Move to new group* from a row's ⋯ menu (or Shift+F10 on it) to make the first one; a group header's menu (right-click, Shift+F10 or its ⋯ glyph) renames it (also F2), reorders or deletes it, rows move between groups from their own menu or by dragging with a mouse or pen, and a collapsed group stays collapsed on that device. **Search sessions** at the top of the rail narrows it to the tabs whose name matches (a web tab by its title), across every group, collapsed ones included, without changing the groups or the order; a tab with an alert stays visible even when its name does not match; dragging rows is off until you clear it; Escape or × clears it, and it is never saved. Desktop and tablet only. |
+| **Vertical rail**    | The strip turned vertical beside the terminal, resizable, with detailed rows by default. **Vertical Rail Order** sorts it by activity (blocked on you first, then longest running, then most recently quiet), the same order as the home screens; pick *Manual* to get your own order and drag-reordering back. **Tab groups:** pick *Move to new group* from a row's ⋯ menu (or Shift+F10 on it) to make the first one; a group header's menu (right-click, Shift+F10 or its ⋯ glyph) renames it (also F2), reorders or deletes it, rows move between groups from their own menu or by dragging with a mouse or pen, and a collapsed group stays collapsed on that device. **Search sessions** at the top of the rail narrows it to the tabs whose name matches (a web tab by its title), across every group, collapsed ones included, without changing the groups or the order; a tab with an alert stays visible even when its name does not match; reordering rows by dragging is off until you clear it, though a found tab can still be dragged onto the tile grid; Escape or × clears it, and it is never saved. Desktop and tablet only. |
 
 It is the same list either way, just re-hosted: tab order, drag-to-reorder, the `Alt+1`
 to `Alt+9` numbers and every status colour below behave identically in both. The setting is