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/pages/Workspace.tsx

@@ -47,6 +47,7 @@ import { useCallback, useEffect, useMemo, useState, useSyncExternalStore } from
 import { useLocation, useSearchParams } from "react-router-dom";
 import { useTranslation } from "react-i18next";
 import {
+  ArrowLeft,
   Plus,
   Square,
   Columns2,
@@ -79,6 +80,8 @@ import LaneCard, {
 import { AddLaneModal } from "../components/lanes/AddLaneModal";
 import { LaneChangesPanel } from "../components/lanes/LaneChangesPanel";
 import { WorkspaceSessionsTab } from "../components/lanes/WorkspaceSessionsTab";
+import { WorkspaceHome } from "../components/lanes/WorkspaceHome";
+import { DestructiveLaneModal } from "../components/lanes/DestructiveLaneModal";
 import { readSplitViewState, writeSplitViewState } from "../lib/splitViewStorage";
 import type { SplitViewState, SplitLayout } from "../lib/splitViewStorage";
 
@@ -373,6 +376,8 @@ export function Workspace() {
       setSearchParams(
         (prev) => {
           const next = new URLSearchParams(prev);
+          // A run belongs to its lane: another lane opens on its home.
+          if (next.get("lane") !== String(id)) next.delete("run");
           if (id === null) next.delete("lane");
           else next.set("lane", String(id));
           return next;
@@ -394,6 +399,10 @@ export function Workspace() {
     if (paramId === null) setSelectedLaneId(selectedLaneId);
   }, [lanesLoaded, selectedLaneId, paramId, setSelectedLaneId]);
   const [laneActionError, setLaneActionError] = useState<string | null>(null);
+  const [destructive, setDestructive] = useState<{
+    lane: Lane;
+    action: "reset" | "remove";
+  } | null>(null);
   const [addLaneOpen, setAddLaneOpen] = useState(false);
   // Fields the Add-lane modal opens with when it was opened from a lane's git
   // bar ("new lane here"): one provisioning path for every lane, prefilled.
@@ -664,8 +673,12 @@ export function Workspace() {
   // so the form is fully reachable on short windows. A full-width Changes panel
   // hides that form anyway, and without a locked height it shrinks to its
   // content — the editor inside it collapsed to a few lines (no live run).
+  // A workspace opens on its HOME (WorkspaceHome); `?run=` opens a session —
+  // the console, panes and Changes panel, which the home only hides (CSS), so
+  // a live terminal never unmounts behind it.
+  const home = !!currentLane && !runParam;
   const viewportLocked =
-    paneHasActiveRun || (!!currentLane && changesOpen && changesSize === "full");
+    !home && (paneHasActiveRun || (!!currentLane && changesOpen && changesSize === "full"));
 
   const handleLaneAction = async (id: number, action: string, body?: Record<string, unknown>) => {
     setLaneActionError(null);
@@ -767,7 +780,26 @@ export function Workspace() {
             it rather than under it. It collapses to a rail instead of
             unmounting nothing — there is no live subscription inside it, so
             unmounting is safe and keeps a closed panel from polling. */}
-        <div className="flex min-h-0 flex-1 gap-4">
+        {home && currentLane && (
+          <WorkspaceHome
+            lane={currentLane}
+            onRenamed={() => void refreshLanes()}
+            onMenuAction={(action) => {
+              if (action === "new-here") {
+                setAddLanePrefill({ sourceRepo: currentLane.source_repo || currentLane.cwd });
+                setAddLaneOpen(true);
+              } else if (action === "reset" || action === "remove") {
+                setDestructive({ lane: currentLane, action });
+              } else if (action === "started") {
+                setSearchParams({
+                  lane: String(currentLane.id),
+                  run: `agenthub-lane-${currentLane.id}`,
+                });
+              }
+            }}
+          />
+        )}
+        <div className={`flex min-h-0 flex-1 gap-4${home ? " hidden" : ""}`}>
           <section
             data-testid="lane-detail"
             className={`flex min-h-0 min-w-0 flex-1 flex-col ${currentLane ? "card p-4" : ""}${
@@ -790,8 +822,18 @@ export function Workspace() {
                     ? tLanes("statusDead")
                     : tLanes(`status.${currentLane.status}`, { defaultValue: currentLane.status })}
                 </span>
-                {/* Renaming lives on the sidebar row (double-click); here the
-                  name is only read. */}
+                {/* Back to the workspace's home; renaming lives on the sidebar
+                  row and the home's title, so here the name is only read. */}
+                <button
+                  type="button"
+                  data-testid="workspace-back-home"
+                  onClick={() => setSearchParams({ lane: String(currentLane.id) })}
+                  title={tLanes("home.back")}
+                  aria-label={tLanes("home.back")}
+                  className="shrink-0 rounded p-0.5 text-fg-muted hover:bg-surface-4 hover:text-fg-primary"
+                >
+                  <ArrowLeft className="h-4 w-4" />
+                </button>
                 <span
                   title={currentLane.cwd}
                   className="min-w-0 truncate text-sm font-semibold text-fg-primary"
@@ -1086,6 +1128,31 @@ export function Workspace() {
         }}
       />
 
+      {destructive && (
+        <DestructiveLaneModal
+          lane={destructive.lane}
+          action={destructive.action}
+          open
+          onClose={() => setDestructive(null)}
+          onConfirm={async (body) => {
+            const { lane, action } = destructive;
+            setDestructive(null);
+            setLaneActionError(null);
+            try {
+              await api.lanes.action(lane.id, action, {
+                confirm: true,
+                expect: body.expect,
+                ...(body.force === true ? { force: true } : {}),
+              });
+              await refreshLanes();
+              if (action === "remove") setSearchParams({});
+            } catch (err) {
+              setLaneActionError(err instanceof Error ? err.message : String(err));
+            }
+          }}
+        />
+      )}
+
       {laneActionError && (
         <p
           role="alert"