chat: mission mode (/mission, --mission) — autonomous goal runs in background with retries, corrections, state-aware retry hints; input() moved to thread so missions run while the REPL waits; configurable nudge_limit

testbed/README.md

@@ -82,9 +82,19 @@ you> иди к маяку            → look_at + move step by step (auto-conti
 you> повернись налево       → turn(-90)
 you> осмотрись              → vision + description
 you> активируй маяк         → interact (when close)
+you> /mission               → autonomous goal: reach & activate the beacon,
+                             keeps trying until done (retries + corrections)
+you> /mission дойди до маяка
+you> /status  /stop         → mission progress / cancel
 you> /state  /look  /map  /models  /model gemma4:12b  /steps N  /help  /exit
 ```
 
+Missions run in the background while the REPL stays usable — watch the
+capsule on http://127.0.0.1:8000 as it works. Start one directly:
+`python -m testbed.chat --mission [--mission-steps 50] [--mission-retries 3]`.
+The mission keeps trying (corrections when it drifts, nudges when it stalls,
+fresh attempts on failure) until the goal is achieved; `/stop` cancels it.
+
 Each turn's transcript is printed; the current frame lands in `chat_frame.png`
 and the sensor-built map in `chat_map.png`. Any OpenAI-compatible endpoint
 works: `python -m testbed.chat --base-url https://api.openai.com/v1