CLI: rename heartbeat tmux helper and log file path

docs/tmux.md

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+# tmux helpers (relay backgrounding)
+
+## Why we ship tmux helpers
+- Run the relay detached so your shell can close, while keeping an interactive pane you can reattach to.
+- Provide a consistent start/attach workflow without adding a daemon mode or external process manager.
+- Keep the relay code itself tmux-agnostic; tmux is only a launcher concern.
+
+## Commands
+- `warelay relay:tmux` — restarts the `warelay-relay` session running `pnpm warelay relay --verbose`, then attaches (skips attach when stdout isn’t a TTY).
+- `warelay relay:tmux:attach` — attach to the existing session without restarting it.
+- `warelay relay:heartbeat:tmux` — same as `relay:tmux` but adds `--heartbeat-now` so Claude is pinged immediately on startup.
+
+All helpers use the fixed session name `warelay-relay`.
+
+## Logs
+- The relay always writes to the configured file logger (defaults to `/tmp/warelay/warelay.log`); on start it prints the active log path and level.
+- tmux is just for interactive viewing; you can also tail the log file or use another supervisor if you prefer.