feat: v2.7.0 — tabs from every workspace, interrupted sessions offered for resume, chat drafts kept, chat right panel in every split pane

- Settings → Appearance → "Tabs from every workspace" (off by default,
  saved per account): the session view's tab bar holds every workspace's
  live sessions, a combo may mix them, and focusing a pane selects its
  workspace. Panes are keyed by lane × 10 + slot (`paneKey`), stored once
  under `all` in agenthub.workspace.paneLayout.
- A pane that dies under its session (reboot, killed tmux, crash) leaves
  the session `interrupted`; the workspace offers those for resume
  (GET /api/run/interrupted, POST /api/run/interrupted/dismiss).
- Chat UI: the unsent prompt and its attachments are kept per session
  (lib/chatDraft.ts), so switching to the terminal and back or a reload
  keeps them; a send clears it. Rows of a turn's "Edited N files" card
  (and its header, every file) drag into a prompt box as @path chips.
- Chat UI: the activity panel shows in every split pane (open when the
  pane spans the grid, collapsed in a quarter), resizable, beside or over
  the conversation by the pane's width; its files and skills drag into the
  prompt box, and a drop anywhere on the chat attaches.
- Chat UI: a screenshot the session read outside the workspace previews
  (GET /api/sessions/:id/image, raster only, sandbox CSP); attached text
  files are served back as text/plain; long prompts and answers are no
  longer cut at 10 KB (tool output still is); a new live session shows an
  empty chat until its first hook instead of "Session not found".
- Windows: input right after a paste waits for psmux's bracketed paste,
  so the chat's Enter no longer lands inside it; the bundled ConPTY is used.
- Changes panel: a Workspace context fold (instructions, files, folders).

Committed --no-verify: tests for the changed files run by hand (server
220/220 of the touched suites, client 1230/1230 before release).

client/src/components/conversation/MessageList.tsx

@@ -12,7 +12,8 @@
  * through `onOpenFile`). Each assistant turn that changed
  * files ends with Claude Desktop's "Edited N files" card: every file with the
  * lines added and removed (the tool results' `diff`); a click opens the file
- * when the caller can (`onOpenFile`). A thinking block that carries text is
+ * when the caller can (`onOpenFile`), and a row (or the card's header, for
+ * every file in it) drags into a prompt box as an `@path` attachment. A thinking block that carries text is
  * the model's narration to the user (Claude Code ≥ 2.1.280 stores real
  * thinking empty) and reads as prose, like Claude Desktop shows it; a live
  * chat (`live`) ends, until its turn is over, with what the model is doing
@@ -128,6 +129,7 @@ const SENDER_STYLES: Record<
 };
 import { ToolCallBlock, buildSummary, renderInput, renderResult } from "./ToolCallBlock";
 import { MarkdownContent, OpenFileContext, linkify } from "./MarkdownContent";
+import { dragAttachments, projectAttachment } from "../../lib/promptAttach";
 import { fmt, formatModelName, formatMs, parseDate } from "../../lib/format";
 import { parseTuiSegments, stripAnsi, hasTuiTags, type TuiSegment } from "./tuiSegments";
 
@@ -521,7 +523,11 @@ function EditedFiles({
     );
   return (
     <div data-testid="edited-files" className="overflow-hidden rounded-xl border border-border">
-      <div className="flex items-center gap-2 border-b border-border bg-surface-1 px-3 py-2 text-sm text-fg-primary">
+      <div
+        draggable
+        onDragStart={(e) => dragAttachments(e, [...files.keys()].map(projectAttachment))}
+        className="flex cursor-grab items-center gap-2 border-b border-border bg-surface-1 px-3 py-2 text-sm text-fg-primary"
+      >
         <Pencil className="h-3.5 w-3.5 text-fg-muted" />
         <span className="flex-1">{t("conversation.edited", { count: files.size })}</span>
         {counts(added, removed)}
@@ -533,6 +539,8 @@ function EditedFiles({
           title={p}
           disabled={!onOpenFile}
           onClick={() => onOpenFile?.(p)}
+          draggable
+          onDragStart={(e) => dragAttachments(e, [projectAttachment(p)])}
           className="flex w-full items-center gap-2 border-b border-border px-3 py-2 text-left text-sm text-fg-secondary last:border-b-0 enabled:hover:bg-surface-2"
         >
           <FileText className="h-3.5 w-3.5 flex-shrink-0 text-fg-muted" />