docs: refactor docs structure and tighten assistant instruction policy

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

scripts/test-hdmi-cec.sh

@@ -65,6 +65,8 @@ while true; do
     echo "  4) Scan for devices"
     echo "  5) Test Display Manager CEC integration"
     echo "  6) View CEC logs from Display Manager"
+    echo "  7) Show power intent/state runtime files"
+    echo "  8) Clear power intent/state runtime files"
     echo "  q) Quit"
     echo ""
     read -p "Enter choice: " choice
@@ -249,6 +251,35 @@ PYTEST
             echo ""
             read -p "Press Enter to continue..."
             ;;
+        7)
+            echo -e "${YELLOW}Showing power intent/state runtime files...${NC}"
+            echo ""
+            INTENT_FILE="$PROJECT_ROOT/src/power_intent_state.json"
+            STATE_FILE="$PROJECT_ROOT/src/power_state.json"
+
+            if [ -f "$INTENT_FILE" ]; then
+                echo "power_intent_state.json:"
+                echo "-------------------------"
+                cat "$INTENT_FILE"
+            else
+                echo "power_intent_state.json not found"
+            fi
+            echo ""
+            if [ -f "$STATE_FILE" ]; then
+                echo "power_state.json:"
+                echo "-----------------"
+                cat "$STATE_FILE"
+            else
+                echo "power_state.json not found"
+            fi
+            echo ""
+            read -p "Press Enter to continue..."
+            ;;
+        8)
+            echo -e "${YELLOW}Clearing power intent/state runtime files...${NC}"
+            rm -f "$PROJECT_ROOT/src/power_intent_state.json" "$PROJECT_ROOT/src/power_state.json"
+            echo -e "${GREEN}Removed runtime power files (if present).${NC}"
+            ;;
         q|Q)
             echo "Exiting..."
             exit 0