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/lib/promptAttach.ts

@@ -2,7 +2,8 @@
  * @file promptAttach.ts
  * @description What a prompt box can attach besides a fresh upload: a project
  * file or folder dragged from the Files panel (`ATTACH_MIME`, read back by
- * `PromptEditor`'s drop) and the files uploaded through a prompt box in the
+ * `PromptEditor`'s drop) or from a Chat pane's activity panel
+ * (`dragAttachments`, `dragSkill`: a skill becomes the prompt's `/command`) and the files uploaded through a prompt box in the
  * last day (`recentUploads`, kept in this browser). An attachment is a path
  * sent with the prompt, so nothing here touches the server.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
@@ -26,21 +27,59 @@ export function projectAttachment(rel: string): Attachment {
 }
 
 /** Start a drag carrying `rel` (a Files panel row) to a prompt box; plain
- *  text too, so a drop elsewhere (a terminal, an editor) gets the path. */
+ *  text too, so a drop elsewhere (a terminal, an editor) gets the path. A row
+ *  under a `data-drag-root` (an extra folder's section) lies outside the
+ *  pane's folder, so it carries its absolute path instead. */
 export function dragProjectPath(e: DragEvent, rel: string) {
-  e.dataTransfer.setData(ATTACH_MIME, JSON.stringify(projectAttachment(rel)));
-  e.dataTransfer.setData("text/plain", rel);
+  const root = (e.currentTarget as HTMLElement | null)?.closest?.<HTMLElement>("[data-drag-root]")
+    ?.dataset.dragRoot;
+  const path = root ? `${root.replace(/[\\/]+$/, "")}/${rel}` : rel;
+  e.dataTransfer.setData(ATTACH_MIME, JSON.stringify(projectAttachment(path)));
+  e.dataTransfer.setData("text/plain", path);
   e.dataTransfer.effectAllowed = "copy";
 }
 
-/** The attachment a drop carries, if it is one of ours. */
-export function droppedAttachment(dt: DataTransfer | null | undefined): Attachment | null {
+/** Start a drag carrying attachments as they are (an activity panel's files,
+ *  already absolute); plain text too, like `dragProjectPath`. */
+export function dragAttachments(e: DragEvent, items: Attachment[]) {
+  e.dataTransfer.setData(ATTACH_MIME, JSON.stringify(items));
+  e.dataTransfer.setData("text/plain", items.map((a) => a.path.replace(/^@/, "")).join(" "));
+  e.dataTransfer.effectAllowed = "copy";
+}
+
+/** The attachments a drop carries, if they are ours: one, or a list. */
+export function droppedAttachments(dt: DataTransfer | null | undefined): Attachment[] {
   try {
     const v: unknown = JSON.parse(dt?.getData(ATTACH_MIME) || "null");
-    const a = v as Attachment | null;
-    return a && typeof a.path === "string" && typeof a.name === "string"
-      ? { path: a.path, name: a.name }
-      : null;
+    return (Array.isArray(v) ? v : [v])
+      .filter(
+        (a): a is Attachment =>
+          !!a &&
+          typeof (a as Attachment).path === "string" &&
+          typeof (a as Attachment).name === "string"
+      )
+      .map((a) => ({ path: a.path, name: a.name }));
+  } catch {
+    return [];
+  }
+}
+
+export const SKILL_MIME = "application/x-agenthub-skill";
+// A skill's name as Claude Code types it: `name` or `plugin:name`.
+const SKILL_RE = /^[\w.-]+(?::[\w.-]+)?$/;
+
+/** Start a drag carrying a skill; dropped on a prompt box it becomes `/name`. */
+export function dragSkill(e: DragEvent, name: string) {
+  e.dataTransfer.setData(SKILL_MIME, name);
+  e.dataTransfer.setData("text/plain", `/${name}`);
+  e.dataTransfer.effectAllowed = "copy";
+}
+
+/** The skill a drop carries, if it is one of ours. */
+export function droppedSkill(dt: DataTransfer | null | undefined): string | null {
+  try {
+    const name = dt?.getData(SKILL_MIME) ?? "";
+    return SKILL_RE.test(name) ? name : null;
   } catch {
     return null;
   }