bug(dispatch): Grid Dispatch first lanes lost their selector strip when the index began following focus #850

Expected behavior

In Grid Dispatch, every lane can be switched to a different agent with one click on a selector that belongs to that lane, so moving between agents in any lane is a single gesture.

Actual behavior

The first (leftmost) lane of every Grid Dispatch row has no compact index strip. Every other lane has one.

How it got that way (corrected; see the comment below):

• Before Grid Dispatch, one sidebar index always wrote lane 0, so lane 0 correctly had no strip.
• feat(dispatch): grid dispatch mode with per-row projects and no self-filling slots #687 (524671b2) made the index per-row and made it fill whichever lane of its row is focused. For that reason it gave every lane a strip.
• fix(dispatch): wake a hibernated agent before placing it in a Grid Dispatch lane #691 (1eb9a472, a lane-wake fix) removed the first lane's strip as a side change, arguing that the index "IS its selector". That was already false, because the index followed focus.

So the first lane now has no selector of its own. To change the agent in it you have to click into the lane first to move focus, then pick from the index. Every other lane takes one click on its strip.

Reproduction

1. Enter Dispatch and switch to Grid Dispatch with a row of two or more lanes.
2. Focus lane 2 of a row.
3. Try to change the agent shown in lane 1 of the same row.
4. There is no strip beside lane 1. Clicking an agent in the row's index replaces lane 2 (the focused lane), not lane 1.

Evidence

• src/renderer/src/workspace/dispatch/TiledDispatchLayout.tsx renders DispatchMiniList only for column > 0. The WHY comment still argues that the row's index "is its selector".
• The same file's selectIntoRow targets focusedLaneInRow ?? start, introduced in 524671b (feat(dispatch): grid dispatch mode with per-row projects and no self-filling slots #687), which also rendered a strip on every lane. 1eb9a47 (fix(dispatch): wake a hibernated agent before placing it in a Grid Dispatch lane #691) restored the column > 0 gate.
• gridDispatchLayout.renderer.test.tsx pins the old rule ("leaves each row's FIRST lane to that row's index list").

Related, same JSX: the empty-lane hint branches on gridRow.projectTabId, the legacy single binding that normalizeGridShape folds into projectTabIds on read. That read is always undefined, so the branch is dead. It is harmless, though: it was added in 524671b to withhold "⌥↓ for the top of the index" from bound rows while ⌥↓ still walked the global list, and 29ecd82 has since made ⌥↓ row-scoped (tiledRowScopedRows), so the copy the dead read falls through to is correct in every row. The fix deletes the branch rather than "correcting" the read, which would withhold a true promise.

Impact

Navigation regression in the main multi-agent layout. The leftmost lane of each row is also the widest by default, so it is where the user most often wants to swap agents.

Environment

Agent Code 0.0.2-beta.1, main at 037da45.