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The READMEs never said tmux was needed, so a fresh install only found out when Start Run failed with nothing explaining why. Both doctors were silent about it too. - README/README.vi: a prerequisites table (node, npm, git, tmux, claude, codex, gh, systemd) and per-OS tmux install + verify steps; the feature list is regrouped into observe/drive/configure and now covers analytics, alerts, import, remote sources, the config explorer and Update all. - INSTALL: Step 0 for the system packages, plus a troubleshooting entry separating "tmux missing" from "the server has a different PATH". - SETUP/docs/README: the same troubleshooting entry and a pointer to Step 0. - plugin-doctor: a tmux row, WARN and never FAIL - the run console and `lanes shell` break without it, nothing else does. Reuses tmux.js's own isTmuxAvailable(). - agenthub doctor: asks GET /api/run/tmux instead, because the PATH that decides whether a run starts is the server's, not the caller's shell's.