feat: add FDIR fault counter and wire it into the MGM device handler

Add satrs::fdir::FaultCounter, an FSFW-style error threshold counter:
counts faults, decrements over time when faults stop, and reports
when a threshold is exceeded. Two variants for now, mirroring the
hk.rs helper pattern:
- FaultCounterStd, backed by std::time::Instant
- FaultCounterEmbassy, backed by embassy_time::Instant (embassy-time
  feature), with an optional defmt::Format impl gated on the defmt
  feature

Add satrs::health::HealthTableMapSync::default() for easy construction
of a shared, global health table.

Wire both into the example app's MGM device handler as the first real
FDIR use case:
- the minisim MGM model gains SpiFaultMode (None/AllZeros/AllOnes) and
  a SetSpiFault request, so a stuck SPI bus can be injected for testing,
  independent of switch state
- MgmHandlerLis3Mdl::poll_sensor checks the SPI transfer result: a
  comm timeout or an all-1s stuck-bus reply (the same pattern the sim
  already uses for "device off") counts as a fault. Above threshold,
  the component is marked Faulty in a HealthTableMapSync shared from
  main.rs. This logic lives in the device handler, not the SPI comm
  layer, since deciding what a failed transfer means for FDIR is a
  handler concern.
- an all-0s reply is deliberately not treated as a fault, since it
  collides with a legitimate zero-field reading

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BaKjBjnxaHJ6vzficJcjN4

satrs-example/types/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2024"
 [dependencies]
 serde = { version = "1", features = ["derive"] }
 spacepackets = { version = "0.18", default-features = false }
-satrs = { path = "../../satrs" }
+satrs = { path = "../../satrs", features = ["serde"] }
 num_enum = { version = "0.7" }
 strum = { version = "0.28", features = ["derive"] }
 postcard = { version = "1" }

satrs-example/types/src/acs/mgm.rs

@@ -7,6 +7,13 @@ pub mod request {
         ReadMode,
     }
 
+    #[derive(serde::Serialize, serde::Deserialize, Debug, Clone, Copy, PartialEq, Eq)]
+    pub enum HealthRequest {
+        /// Overrides the device's autonomous FDIR health state, for example to clear a `Faulty`
+        /// state set by the handler after ground has fixed or worked around the underlying issue.
+        SetHealth(satrs::health::HealthState),
+    }
+
     #[derive(Debug, PartialEq, Eq, Clone, Copy, serde::Serialize, serde::Deserialize)]
     pub enum HkId {
         Sensor,
@@ -23,6 +30,7 @@ pub mod request {
         Ping,
         Hk(HkRequest),
         Mode(ModeRequest),
+        Health(HealthRequest),
     }
 
     impl Request {
@@ -31,6 +39,7 @@ pub mod request {
                 Request::Ping => crate::MessageType::Verification,
                 Request::Hk(_hk_request) => crate::MessageType::Hk,
                 Request::Mode(_mode) => crate::MessageType::Mode,
+                Request::Health(_health) => crate::MessageType::Health,
             }
         }
     }

satrs-example/types/src/lib.rs

@@ -150,6 +150,7 @@ pub enum MessageType {
     Action,
     Event,
     Verification,
+    Health,
 }
 
 pub trait Message {