Vendor the ASN.1 modules the codecs are verified against; untrack IDE churn

asn1/
Three tests assert exact bytes - CamEncodeGoldenTest, DenmAirReceiveTest and
SpatemUperCodecTest - and their expected values came from asn1tools compiled
against ETSI modules that existed only as an untracked working copy on one
machine. A golden-byte fixture nobody else can regenerate is a fixture nobody
can safely touch, so the modules are now in the repo.

Only the seven .asn files those tests need are copied, 576 KB of a 4.2 MB
checkout; the upstream Rust parser is not used by this project at all. Verified
sufficient in isolation: copied into an empty directory, all three specs compile
and reproduce the committed golden CAM bytes byte-identically.

Source is consider it GmbH's C-ITS-Parser (github.com/consider-it/C-ITS-Parser)
at f457426, MIT licensed - LICENSE is retained alongside as that requires. The
schemas themselves are ETSI's standard definitions; upstream's contribution is
assembling them into a compilable set. asn1/README.md records the provenance,
which module pairs with which message, and the rule that matters: never
regenerate a golden fixture from this project's own encoder, because sharing a
mistake between encoder and decoder is exactly the failure these files exist to
catch.

Doc references in the codecs and tests now point at asn1/ instead of the
untracked checkout, and C-ITS-Parser/ is gitignored so the working copy beside
the project is never picked up.

Untracked local state
- .idea/deploymentTargetSelector.xml rewrites itself on every deploy, so it has
  been showing as modified in essentially every commit. Along with
  deviceManager.xml, appInsightsSettings.xml and studiobot.xml it is per-machine
  state, not project configuration.
- obu-firmware/sdkconfig.old is ESP-IDF build output - it is the previous
  sdkconfig, rewritten on every build. sdkconfig.defaults remains tracked, since
  that is the configuration actually chosen.

All five stay on disk; only the tracking is removed. Also ignores
.claude/settings.local.json, which is per-machine, while leaving the skills
beside it committable as project knowledge.

asn1/denm_1_3_1.asn

@@ -0,0 +1,108 @@
+DENM-PDU-Descriptions {itu-t (0) identified-organization (4) etsi (0) itsDomain (5) wg1 (1) en (302637) denm (1) version (2)
+}
+
+DEFINITIONS AUTOMATIC TAGS ::=
+
+BEGIN
+
+IMPORTS 
+ItsPduHeader, CauseCode, Speed, InformationQuality, ReferencePosition, ClosedLanes, DangerousGoodsExtended, Heading, LanePosition, LightBarSirenInUse, RoadType, HeightLonCarr, PosLonCarr, PosCentMass, PositioningSolutionType, RequestResponseIndication, StationType, SpeedLimit, StationarySince, TimestampIts, WheelBaseVehicle, TurningRadius, PosFrontAx, PositionOfOccupants, Temperature, VehicleMass, VehicleIdentification, EnergyStorageType, ActionID, ItineraryPath, NumberOfOccupants, PositionOfPillars, RelevanceTrafficDirection, RestrictedTypes, Traces, TransmissionInterval, ValidityDuration, RelevanceDistance, EventHistory, TrafficRule, DeltaReferencePosition FROM ITS-Container {
+itu-t (0) identified-organization (4) etsi (0) itsDomain (5) wg1 (1) ts (102894) cdd (2) version (2) 
+};
+
+
+DENM ::= SEQUENCE {
+	header ItsPduHeader,
+	denm DecentralizedEnvironmentalNotificationMessage
+}
+
+DecentralizedEnvironmentalNotificationMessage ::= SEQUENCE {
+	management ManagementContainer,
+	situation SituationContainer OPTIONAL,
+	location LocationContainer OPTIONAL,
+	alacarte AlacarteContainer OPTIONAL
+}
+
+ManagementContainer ::= SEQUENCE {
+	actionID ActionID,
+	detectionTime TimestampIts,
+	referenceTime TimestampIts,
+	termination Termination OPTIONAL,
+	eventPosition ReferencePosition,
+	relevanceDistance RelevanceDistance OPTIONAL,
+	relevanceTrafficDirection RelevanceTrafficDirection OPTIONAL,
+	validityDuration ValidityDuration DEFAULT defaultValidity,
+	transmissionInterval TransmissionInterval OPTIONAL,
+	stationType	StationType,
+	...
+}
+
+SituationContainer ::= SEQUENCE {
+	informationQuality InformationQuality,
+	eventType CauseCode,
+	linkedCause CauseCode OPTIONAL,
+	eventHistory EventHistory OPTIONAL,
+	...
+}
+
+LocationContainer ::= SEQUENCE {
+	eventSpeed Speed OPTIONAL,
+	eventPositionHeading Heading OPTIONAL,
+	traces Traces,
+	roadType RoadType OPTIONAL,
+	...
+}
+
+ImpactReductionContainer ::= SEQUENCE {
+	heightLonCarrLeft HeightLonCarr,
+	heightLonCarrRight HeightLonCarr,
+	posLonCarrLeft PosLonCarr,
+	posLonCarrRight PosLonCarr,
+	positionOfPillars PositionOfPillars,
+	posCentMass PosCentMass,
+	wheelBaseVehicle WheelBaseVehicle,
+	turningRadius TurningRadius,
+	posFrontAx PosFrontAx,
+	positionOfOccupants PositionOfOccupants,
+	vehicleMass VehicleMass,
+	requestResponseIndication RequestResponseIndication
+}
+
+RoadWorksContainerExtended ::= SEQUENCE {
+	lightBarSirenInUse LightBarSirenInUse OPTIONAL,
+	closedLanes ClosedLanes OPTIONAL,
+	restriction RestrictedTypes OPTIONAL,
+	speedLimit SpeedLimit OPTIONAL,
+	incidentIndication CauseCode OPTIONAL,
+	recommendedPath ItineraryPath OPTIONAL,
+	startingPointSpeedLimit DeltaReferencePosition OPTIONAL,
+	trafficFlowRule TrafficRule OPTIONAL,
+	referenceDenms ReferenceDenms OPTIONAL
+ }
+
+StationaryVehicleContainer ::= SEQUENCE {
+	stationarySince StationarySince OPTIONAL,
+	stationaryCause CauseCode OPTIONAL,
+	carryingDangerousGoods DangerousGoodsExtended OPTIONAL,
+	numberOfOccupants NumberOfOccupants OPTIONAL,
+	vehicleIdentification VehicleIdentification OPTIONAL,
+	energyStorageType EnergyStorageType OPTIONAL
+}
+
+AlacarteContainer ::= SEQUENCE {
+	lanePosition LanePosition OPTIONAL,
+	impactReduction ImpactReductionContainer OPTIONAL,
+	externalTemperature Temperature OPTIONAL,
+	roadWorks RoadWorksContainerExtended OPTIONAL,
+	positioningSolution PositioningSolutionType OPTIONAL,
+	stationaryVehicle StationaryVehicleContainer OPTIONAL,
+	...
+}
+
+defaultValidity INTEGER ::= 600
+
+Termination ::= ENUMERATED {isCancellation(0), isNegation (1)}
+
+ReferenceDenms ::= SEQUENCE (SIZE(1..8, ...)) OF ActionID
+
+END