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/settings.json

@@ -649,8 +649,7 @@
       "general": "General",
       "agents": "Agents",
       "routing": "Routing",
-      "git": "Git",
-      "projects": "Projects"
+      "git": "Git"
     },
     "section": {
       "general": {
@@ -694,10 +693,7 @@
       },
       "worktrees": {
         "title": "Worktrees",
-        "description": "Which git worktrees the sidebar lists under each project."
-      },
-      "project": {
-        "description": "This project's workspaces and worktree settings."
+        "description": "Which untracked git worktrees a workspace's Add folder suggests."
       }
     }
   },
@@ -706,32 +702,13 @@
     "noMatch": "No setting matches “{{query}}”."
   },
   "worktrees": {
-    "title": "Untracked worktrees",
-    "description": "A worktree with no workspace on it is listed under its project with an Adopt button. Saved in this browser only.",
+    "title": "Worktree suggestions",
+    "description": "When you add a folder to a workspace, the repo's worktrees that have no workspace are suggested. Saved in this browser only.",
     "showUntracked": "Show untracked worktrees",
-    "showUntrackedDesc": "List a repository's worktrees that have no workspace yet.",
+    "showUntrackedDesc": "Suggest a repository's worktrees that have no workspace yet.",
     "claude": "Claude Code worktrees",
     "claudeDesc": "Worktrees under <repo>/.claude/worktrees/, made by Claude Code's own agents.",
     "agenthub": "AgentHub-managed worktrees",
     "agenthubDesc": "Worktrees AgentHub created under its workspaces root."
-  },
-  "project": {
-    "notFound": "No such project.",
-    "facts": "Project",
-    "root": "Root",
-    "mainBranch": "Main branch",
-    "worktreeCount": "Worktrees",
-    "workspaces": "Workspaces",
-    "noWorkspaces": "No workspace in this project yet.",
-    "sources": "Worktree sources",
-    "sourcesDesc": "Override the Worktrees page for this project only.",
-    "override": "Use this project's own setting",
-    "forget": "Forget workspaces",
-    "forgetDesc": "Remove every workspace of this project from AgentHub. Working trees, branches and data on disk are left alone.",
-    "forgetAll": "Forget all workspaces…",
-    "forgetTitle": "Forget {{count}} workspaces?",
-    "forgetBody": "AgentHub drops its record of each one and stops its runs. Nothing on disk is deleted.",
-    "forgetConfirm": "Forget all",
-    "forgetFailed": "Could not forget {{lane}}: {{message}}"
   }
 }