shrink root README into a landing page with a docs map and focused contributor guidance
add TV_POWER_RUNBOOK as the canonical TV power rollout and canary runbook
add CHANGELOG and move project history out of README-style docs
refactor src README into a developer-focused guide (architecture, runtime files, MQTT, debugging)
prune redundant older HDMI docs and keep a canonical HDMI_CEC_SETUP path
update copilot instructions to a high-signal policy format with strict anti-shadow-README design rules
align references across docs to current files, scripts, and TV power behavior
Switch to Paho v2 callbacks; add loop_start() and reconnect_delay_set() for auto-reconnect
Rework on_connect/on_disconnect to v2 signatures; handle session_present and reconnection flows
Gate heartbeats with client.is_connected() and add short retry on rc=4 (NO_CONN)
Re-send discovery after reconnect; ensure re-subscription to all topics
Add startup terminal message with ISO timestamp in simclient.py
Docs: update README and Copilot instructions with reconnection/heartbeat guidance and benign rc=4 notes
