Fix SENSOR power saving deep sleep truncating TX and skipping sleep on failed reads (#10939)

* Fix SENSOR power saving deep sleep behavior

Deep sleep could be entered while a telemetry packet was still queued
or on air, truncating the transmission. canSleep() gained a deepSleep
parameter and now vetoes in that case; light sleep is unchanged.
Telemetry modules defer a pending deep sleep (bounded to 30s) until the
radio is idle and no longer let the sensor polling interval override
the 5s pre-sleep grace period. A failed sensor read still arms deep
sleep instead of leaving the node awake for a full telemetry interval.

Fixes #10890
Fixes #10932

* Deduplicate telemetry deep sleep deferral logic

Move the radio-busy deferral and its counter into BaseTelemetryModule
and add an isPowerSavingSensor() helper. Removes the telemetry-specific
counter from OSThread. The sleep arming block stays per module because
it needs protected OSThread members not visible to the base class.

src/sleep.h

@@ -23,8 +23,18 @@ void initDeepSleep();
 
 void setCPUFast(bool on);
 
-/** return true if sleep is allowed right now */
-bool doPreflightSleep();
+/** return true if sleep is allowed right now
+ * @param deepSleep true when the hardware (radio) is about to be powered down (deep sleep or
+ * shutdown), false for a light sleep where the radio keeps running. Observers may veto more
+ * aggressively for deep sleep, e.g. while a LoRa transmission is still in flight.
+ */
+bool doPreflightSleep(bool deepSleep = false);
+
+/// When a power-saving module wants to deep sleep but doPreflightSleep() vetoes it (e.g. the
+/// radio is still transmitting), re-check this often, and give up waiting after this many
+/// attempts so a busy mesh can't keep the node awake forever
+static constexpr uint32_t PREFLIGHT_SLEEP_RETRY_MS = 1000;
+static constexpr uint32_t MAX_PREFLIGHT_SLEEP_DEFERRALS = 30;
 
 extern int bootCount;