chore: v2.8.71 — remote clients (company hub), artifacts shared with chosen people, folders and viewable copies, fixes

Remote clients (docs/plans/remote-clients/README.md, B1–B3 for the Claude pool):
- server/hub/ holds the hub-only code (devices, remote sessions, upload ingest,
  LAN gateway), required only in server mode; hub-boundary.test.js keeps local
  code from importing it.
- A local install enrolls with `agenthub remote login` or Settings → AI tools →
  Company hub; the "Company account" AI Proxy (reserved name agenthub.company)
  sends a session through the hub's gateway, which adds a pool account's token —
  no credential reaches the machine. Only those sessions are uploaded, hourly
  and at their end; secret-shaped strings are redacted on the client.
- Gateway refuses: unknown device (401), a message without a session id, an
  unregistered session under AGENTHUB_REMOTE_GATE=block, a user over quota
  (EQUOTA), a purged session (410). Device tokens 90 days, conversations 30.
- New alert rule type remote_unmonitored: a company-account session its device
  never registered; a late registration clears the flag instead.
- The hub imports a session once per upload round (chunks carry `more`),
  not once per chunk.

Artifacts:
- Share an artifact with chosen people (artifact_shares, PATCH sharedWith,
  GET /api/artifacts/people) besides everyone; a "Shared with you" tab.
  Only the owner or an admin sees or edits who it is shared with; audited.
- Folders: each account's own arrangement (agenthub.artifacts.folders pref).
- A claude.ai page keeps a copy viewable without the publishing account: its
  HTML file (and supporting files) snapshotted at publish, or the copy Claude
  saves for a Doc / Slides / Design in artifacts-export/ (a synchronous
  PostToolUse hint hook, scripts/artifact-export-hint.js, admin switch),
  attached to the page at Stop. Viewed in HtmlFrame's sandbox, Markdown, or
  pdf.js (pdfjs-dist 6.4.299, legacy build, loaded only for a PDF).

Fixes:
- tmux: a cached /proc/<pid>/exe of an exited server falls back to PATH's
  tmux (stop the last pane, start again within 10 s failed with ENOENT).
- shelves: a shelf restores beside changes in other files.
- chat: a finished reply ends the turn even with no hook at all.
- Settings → AI tools: profile list display tweaks.

server/__tests__/tmux.test.js

@@ -408,6 +408,17 @@ describe("our own tmux server: bounded and version-matched", () => {
     assert.equal(calls, after);
   });
 
+  it(
+    "forgets a cached server binary that is gone and runs PATH's tmux",
+    { skip: process.platform !== "linux" || !tmux.isTmuxAvailable() },
+    () => {
+      // The last pane stopped: the cached /proc/<pid>/exe no longer exists.
+      tmux.__setHostBin("/proc/999999999/exe");
+      tmux.serverVersion(); // no server in the test's TMUX_TMPDIR: null, not ENOENT
+      assert.equal(tmux.__hostBin(), "tmux");
+    }
+  );
+
   it("finds the binary of the server listening on our socket from /proc alone", () => {
     const root = fs.mkdtempSync(path.join(os.tmpdir(), "tmux-proc-"));
     const sock = "/tmp/tmux-1000/default";