- BOT_HOP_STEP_MILLIS_DEFAULT 1500 -> 2500
- BOT_HOP_BIAS_MAX_MILLIS 8000 -> 12000
- BOT_RESPONSE_PENDING_TTL_MILLIS 45000 -> 60000
- BOT_PREFS_VERSION 3 -> 4 (forces re-default of hop_step_ms on existing
bots that saved the old 1500 value)
- writeAckResponse + executeTest: drop the literal "ack " prefix so test
responses now start with "@[sender] ..."
Field test showed two bots with token-matching `[1865]` responses both
firing because the far bot scheduled its reply before the near bot's
reply could propagate back through the mesh. New hop step gives ~5-8 s
of margin at the 4-hop boundary.
