hermes -w appended its worktree note to the CLI's own system prompt, which
the gateway-backed CLI never sends. The gateway's workspace block already
detects a linked worktree from the session cwd; its line now carries the
rest of that note: isolated on branch X, changes don't affect the main
tree or other agents, commit/push and open a PR if appropriate. The
primary tree path stays hidden, as the block's existing rule requires.
Because it derives from the session's folder, every surface opened in a
linked worktree (CLI -w, Ink, Desktop, ACP) gets it. New sessions in a
linked worktree get a changed system prompt; existing sessions keep their
pinned workspace snapshot. The dead client-side note in cli.py is left
for a follow-up (cli.py is changed by #138668).
Refs #134889
