feat: v2.6.0 — Chat UI composer (+ menu, project files, activity panel, permission mode, Stop), git on a workspace's extra folders (#70), long paste as a file (#68), S3 server mode (experimental)

Chat UI:
- Each Claude/Codex session keeps its own chat/terminal view; Settings only
  sets how new sessions open.
- Composer + menu: upload, project files and folders (#54, also dragged from
  the Files/Changes tree), context files, recent uploads, skills, plugins.
- Activity side panel (progress, outputs, files read, uploads, memory,
  skills, connectors) with a file preview; edited-file counts per turn.
- Permission-mode chip (Shift+Tab steps, read back from the pane:
  server/lib/pane-mode.js, GET|POST /api/run/:id/permission-mode).
- Stop (Esc) while the main agent works; the status is checked per agent
  (with session_id /api/agents ignores its status filter) and re-read every
  5 s while Stop shows.
- Dropped images shown in the conversation (GET /api/run/drop/:name, the
  requester's own drop dir), full-size viewer.
- A plain-text paste over 5,000 characters is attached as pasted-text.txt,
  so no prompt reaches tmux/argv limits (#68).

Changes panel: every /api/lanes/:id/git* route takes ?source=<lane_sources
id> (sourceFolder; ENOSOURCE otherwise) and a folder picker switches the
whole panel to a workspace's extra folder (#70).

Server mode S3 (one Linux user per account) — experimental, verified with
fake sudo plus a P6 managed-settings spike on a test account:
- member tmux listing runs in the background (cached, 15 s => unknown);
- transcript snapshot copy is async, chunked, temp file + rename;
- Express Layer patch only on Express 4;
- tmux capturePane/sendKey go to the member's own server.

Docs: the multi-user design moved in as docs/plans/server-mode/README.md
(the AgentHub-Server repo is gone); S3-PLAN P6 result; LANES/API/openapi.

client/src/i18n/locales/en/run.json

@@ -85,7 +85,38 @@
   "chat": {
     "placeholder": "Write a message…",
     "send": "Send",
-    "hint": "Enter sends · permission prompts and menus need the terminal (Settings → Appearance → Chat UI)",
-    "notSent": "The terminal is not connected — the message was not sent."
+    "notSent": "The terminal is not connected — the message was not sent.",
+    "stop": "Stop",
+    "notStopped": "The terminal is not connected — nothing was stopped.",
+    "add": "Add files, skills…",
+    "upload": "Upload or add files",
+    "projectFiles": "Project files",
+    "contextFiles": "Context files",
+    "recentUploads": "Recent uploads",
+    "searchFiles": "Search files and folders…",
+    "skills": "Skills",
+    "plugins": "Plugins",
+    "manageSkills": "Manage skills",
+    "managePlugins": "Manage plugins",
+    "none": "Nothing here yet",
+    "fromPlugin": "{{name}} plugin",
+    "modeFailed": "Could not change the permission mode: {{message}}",
+    "outline": {
+      "progress": "Progress",
+      "outputs": "Outputs",
+      "connectors": "Connectors",
+      "empty": "Nothing yet",
+      "hide": "Hide side panel",
+      "show": "Activity panel",
+      "copyPath": "Copy path: {{path}}",
+      "panel": "Session activity panel",
+      "used": "Used in this session",
+      "uploads": "Uploads",
+      "files": "Files read",
+      "memory": "Memory",
+      "close": "Close",
+      "noPreview": "No preview for this file here",
+      "truncated": "Showing the first part of this file"
+    }
   }
 }