docs: add parachute health failsafe documentation

Update safety.md, peripherals/parachute.md, and releases/main.md to document the extended COM_PARACHUTE parameter and the new configurable in-flight failsafe behaviour.

Author: gguidone

docs/en/config/safety.md

@@ -251,6 +251,19 @@ The relevant parameters are shown below:
 | ---------------------------------------------------------------------------- | ---------------------------------------------------------------- |
 | [NAV_TRAFF_AVOID](../advanced_config/parameter_reference.md#NAV_TRAFF_AVOID) | Set the failsafe action: Disabled, Warn, Return mode, Land mode. |
 
+## Parachute Health Failsafe
+
+<Badge type="tip" text="PX4 v1.18" />
+
+The parachute health failsafe is triggered when a [MAVLink parachute](../peripherals/parachute.md) system is missing or unhealthy while the vehicle is armed and airborne.
+
+| Parameter                                                                                          | Description                                                                                                                                           |
+| -------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- |
+| <a id="COM_PARACHUTE"></a>[COM_PARACHUTE](../advanced_config/parameter_reference.md#COM_PARACHUTE) | Parachute system monitoring and failsafe action. `0`: Disabled (default), `1`: Warning only, `2`: Error only, `3`: Return, `4`: Land. |
+
+Values `2`–`4` prevent arming when the parachute system is not present and healthy.
+Values `3`–`4` also trigger the configured failsafe action if the parachute system is missing or unhealthy while airborne.
+
 ## Quad-chute Failsafe
 
 Failsafe for when a VTOL vehicle can no longer fly in fixed-wing mode, perhaps due to the failure of a pusher motor, airspeed sensor, or control surface.

docs/en/peripherals/parachute.md

@@ -73,7 +73,8 @@ You then need to ensure that the parachute pin will be set to a value that will
 
 PX4 will trigger a connected and healthy parachute on failsafe by sending the command [MAV_CMD_DO_PARACHUTE](https://mavlink.io/en/messages/common.html#MAV_CMD_DO_PARACHUTE) with the [PARACHUTE_RELEASE](https://mavlink.io/en/messages/common.html#PARACHUTE_ACTION) action.
 
-MAVLink parachute support is enabled by setting the parameter [COM_PARACHUTE=1](../advanced_config/parameter_reference.md#COM_PARACHUTE).
+MAVLink parachute support is enabled by setting the parameter [COM_PARACHUTE](../advanced_config/parameter_reference.md#COM_PARACHUTE) to a non-zero value.
+The parameter also configures the arming check and in-flight failsafe action when the parachute system is missing or unhealthy (see [Parachute Health Failsafe](../config/safety.md#parachute-health-failsafe)).
 PX4 will then indicate parachute status using the [MAV_SYS_STATUS_RECOVERY_SYSTEM](https://mavlink.io/en/messages/common.html#MAV_SYS_STATUS_RECOVERY_SYSTEM) bit in the [SYS_STATUS](https://mavlink.io/en/messages/common.html#SYS_STATUS) extended onboard control sensors fields:
 
 - `SYS_STATUS.onboard_control_sensors_present_extended`: MAVLink parachute present (based on heartbeat detection).

docs/en/releases/main.md

@@ -42,6 +42,7 @@ Please continue reading for [upgrade instructions](#upgrade-guide).
 
 - [QGroundControl Bootloader Update](../advanced_config/bootloader_update.md#qgc-bootloader-update-sys-bl-update) via the [SYS_BL_UPDATE](../advanced_config/parameter_reference.md#SYS_BL_UPDATE) parameter has been re-enabled after being broken for a number of releases. ([PX4-Autopilot#25032: build: romf: fix generation of rc.board_bootloader_upgrade](https://github.com/PX4/PX4-Autopilot/pull/25032)).
 - [Feature: Allow prioritization of manual control inputs based on their instance number in ascending or descending order](../config/manual_control.md#px4-configuration). ([PX4-Autopilot#25602: Ascending and descending manual control input priorities](https://github.com/PX4/PX4-Autopilot/pull/25602)).
+- [Parachute health failsafe](../peripherals/parachute.md): extended [COM_PARACHUTE](../advanced_config/parameter_reference.md#COM_PARACHUTE) from a boolean into a configurable failsafe parameter. The in-flight action is now selectable (Return or Land). Users previously on `COM_PARACHUTE=1` (block arming) must update to `2` to retain that behaviour; set to `3` or higher to also enable the in-flight failsafe action. ([PX4-Autopilot#26918](https://github.com/PX4/PX4-Autopilot/pull/26918))
 
 ### Control