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/i18n/locales/en/lanes.json

@@ -334,5 +334,35 @@
   "tree.search": "Search workspaces and sessions",
   "tree.newSession": "New session",
   "tree.noSessions": "No sessions yet",
-  "tree.transcriptHint": "No live pane — opens the transcript"
+  "tree.transcriptHint": "No live pane — opens the transcript",
+  "home.breadcrumb": "Workspaces",
+  "home.placeholder": "How can I help you today?",
+  "home.start": "Start",
+  "home.allBusy": "All four panes of this workspace are busy — stop one before starting another session.",
+  "home.recents": "Recents",
+  "home.noRecents": "No sessions yet — start one above.",
+  "home.instructions": "Instructions",
+  "home.instructionsEmpty": "Add instructions to tailor how the agent works in this workspace. They are appended to every new session's system prompt.",
+  "home.edit": "Edit instructions",
+  "home.save": "Save",
+  "home.cancel": "Cancel",
+  "home.memory": "Memory",
+  "home.viewMemory": "View memory",
+  "home.memoryCount_one": "{{count}} file the agent reads",
+  "home.memoryCount_other": "{{count}} files the agent reads",
+  "home.memoryEmpty": "Memory shows here once the folder has a CLAUDE.md or AGENTS.md, or Claude saves memory for it.",
+  "home.context": "Context",
+  "home.contextEmpty": "Add PDFs, documents, or other text to reference in this workspace.",
+  "home.addFile": "Add files",
+  "home.folder": "Folder",
+  "home.ownFolder": "Workspace folder",
+  "home.addFolder": "Add folder",
+  "home.folderPath": "Absolute folder path",
+  "home.add": "Add",
+  "home.suggested": "Untracked worktrees",
+  "home.remove": "Remove",
+  "home.missing": "missing",
+  "home.unsupported": "{{tool}} cannot take instructions, context files or extra folders: they are kept, but its sessions start without them.",
+  "home.back": "Back to the workspace home",
+  "home.close": "Close"
 }