feat(ui): a Claude-Desktop-style home for every workspace

/workspace?lane=<id> opens on the workspace's home (WorkspaceHome): a prompt
box whose Start opens a new session in the first free pane slot, Recents (a
live session attaches its pane, any other opens its transcript, nothing
resumes), and Instructions / Memory / Context / Folder. Instructions live in
lanes.instructions, extra folders and uploaded files in the new lane_sources
table (copies under <data dir>/workspace-context/<lane id>/); spawnRun reads
them from the lane's rows and hands Claude --add-dir + an appended system
prompt file, Codex --add-dir + developer_instructions. Memory is read-only.

Every dashboard pane carries AGENTHUB_RUN_ID; hooks forward it and the run
records which session the pane holds (a Claude pane follows /clear and
/resume but not a nested claude -p), so the sidebar and notifications open
the right pane (&run=). Settings loses its Projects group; Worktrees now
decides which worktrees Add folder suggests.

client/src/components/lanes/WorkspaceSessionList.tsx

@@ -18,6 +18,19 @@ import { timeAgo } from "../../lib/format";
 
 export const SESSION_LIMIT = 20;
 
+/**
+ * The live pane holding a session: the run the hooks bound it to
+ * (`dashboard_runs.session_id`), else — a pane started before the hooks
+ * reported it — the lane's own pane when the lane's bound session is this one.
+ */
+export function liveRunFor(lane: Lane, runs: RunHandle[], sessionId: string): RunHandle | null {
+  const live = runs.filter((r) => r.laneId === lane.id && r.status === "running");
+  return (
+    live.find((r) => r.sessionId === sessionId) ??
+    (lane.session_id === sessionId ? (live.find((r) => r.id === lane.run_id) ?? null) : null)
+  );
+}
+
 export function WorkspaceSessionList({
   lane,
   liveRuns,
@@ -53,8 +66,7 @@ export function WorkspaceSessionList({
   const shown = (sessions ?? []).filter(
     (s) => !q || (s.name ?? "").toLowerCase().includes(q) || s.id.startsWith(q)
   );
-  const runFor = (s: Session) =>
-    liveRuns.find((r) => r.sessionId === s.id && r.status === "running") ?? null;
+  const runFor = (s: Session) => liveRunFor(lane, liveRuns, s.id);
 
   if (sessions !== null && shown.length === 0) {
     return <p className="py-1 pl-8 text-[11px] text-fg-muted">{t("tree.noSessions")}</p>;