feat(tiers): EmbeddedAI on-chain — base_multiplier + subsidy piso EmbeddedArm (#16)

Espejea HardwareTier::EmbeddedAI (Jetson Orin Nano) en el mirror de la cadena,
en lockstep con arkhe-core bbac1b2 (Ergon Fase 1 EmbeddedAI, ADR-0072 / DC 2ba235e1).

Trampa de la fuente preservada byte-fiel: EmbeddedAI APPEND discriminante 4
(SCALE wire-safe, attestations runtime_tier:u8 viejas válidas) PERO rank de
capacidad 1 (entre EmbeddedArm=0 y Portable=2). Por eso Ord es MANUAL por rank()
(no derive — un derive pondría EmbeddedAI > Ultra, falso) y el gating Hero es por
rank, no por discriminante.

- tiers.rs: variant EmbeddedAI (last) + Ord/PartialOrd manual por rank() +
  rank()/ordinal()/from_ordinal() SSOT (el reverse-map que evita perder el
  tier-floor al deserializar, #16) + base_multiplier_x100=10 (piso, el estudiante
  en Jetson no paga más que en Pi 5) + surcharge Hero gated=0 + supports_hero=false.
- fee_schedule.rs: 6 arms EmbeddedAI = piso EmbeddedArm en subsidy_basis_points +
  educational override incluye EmbeddedAI (device de estudiante).
- fees.rs / unified.rs: cobertura — compute_fee(EmbeddedAI)==EmbeddedArm + grid de
  paridad OCAFB-5 extendido a EmbeddedAI.

Tests: 21 suites / 261 workspace verde, 0 regresión. SCALE index == ordinal sellado.
FIX-4 (verificador attestation) ortogonal — no mapea el enum, intacto.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/origin-chain-fees/src/fee_schedule.rs

@@ -87,6 +87,11 @@ pub const fn subsidy_basis_points(hw: HardwareTier, action: ChainAction) -> u32
         (EmbeddedArm, Write) => 9000,
         (EmbeddedArm, Compute) => 10000, // educational compute free
         (EmbeddedArm, Transfer) => 9000,
+        // EmbeddedAI (Jetson Orin Nano): MISMO piso EmbeddedArm — Inmutable #16,
+        // el estudiante en Jetson no paga más que en Pi 5. Ergon bbac1b2.
+        (EmbeddedAI, Write) => 9000,
+        (EmbeddedAI, Compute) => 10000, // educational compute free
+        (EmbeddedAI, Transfer) => 9000,
         // Portable: subsidy media
         (Portable, Write) => 7500,
         (Portable, Compute) => 5000,
@@ -108,6 +113,10 @@ pub const fn subsidy_basis_points(hw: HardwareTier, action: ChainAction) -> u32
         (EmbeddedArm, DeployContract) => 9000,    // Pi 5 dev contracts canonical
         (EmbeddedArm, CallContract) => 10000,     // educational call free
         (EmbeddedArm, UploadContractCode) => 9000, // Pi 5 storage subsidy
+        // EmbeddedAI (Jetson): mismo piso EmbeddedArm en contract actions (#16).
+        (EmbeddedAI, DeployContract) => 9000,     // Jetson dev contracts = piso Pi 5
+        (EmbeddedAI, CallContract) => 10000,      // educational call free
+        (EmbeddedAI, UploadContractCode) => 9000, // Jetson storage subsidy = piso
         (Portable, DeployContract) => 7500,
         (Portable, CallContract) => 5000,
         (Portable, UploadContractCode) => 7500,
@@ -247,11 +256,12 @@ impl OitFeeSchedule for OitFeeScheduleMock {
     }
 
     fn subsidy_eligible(&self, _user_id: &str, action: ChainAction) -> bool {
-        // OCAFB-3 override: educational_world → 100% subsidy EmbeddedArm + Portable
+        // OCAFB-3 override: educational_world → 100% subsidy en los tiers floor
+        // EmbeddedArm + EmbeddedAI + Portable (Jetson = device de estudiante, #16).
         if self.educational_world
             && matches!(
                 self.default_hardware,
-                HardwareTier::EmbeddedArm | HardwareTier::Portable
+                HardwareTier::EmbeddedArm | HardwareTier::EmbeddedAI | HardwareTier::Portable
             )
         {
             return true;
@@ -260,11 +270,11 @@ impl OitFeeSchedule for OitFeeScheduleMock {
     }
 
     fn tier_multiplier(&self, _user_id: &str, action: ChainAction) -> u64 {
-        // Educational override → multiplier 0 (free)
+        // Educational override → multiplier 0 (free) en los tiers floor.
         if self.educational_world
             && matches!(
                 self.default_hardware,
-                HardwareTier::EmbeddedArm | HardwareTier::Portable
+                HardwareTier::EmbeddedArm | HardwareTier::EmbeddedAI | HardwareTier::Portable
             )
         {
             return 0;
@@ -295,6 +305,7 @@ mod tests {
         // Inmutable #37 baseline: Read NEVER charged per HardwareTier
         for hw in [
             HardwareTier::EmbeddedArm,
+            HardwareTier::EmbeddedAI,
             HardwareTier::Portable,
             HardwareTier::Desktop,
             HardwareTier::Ultra,
@@ -303,6 +314,27 @@ mod tests {
         }
     }
 
+    #[test]
+    fn embedded_ai_subsidy_mirrors_embedded_arm_floor_inmutable_16() {
+        // El estudiante en Jetson (EmbeddedAI) no paga MÁS que en Pi 5
+        // (EmbeddedArm): piso idéntico en TODA acción. Ergon bbac1b2, #16.
+        for action in [
+            ChainAction::Read,
+            ChainAction::Write,
+            ChainAction::Compute,
+            ChainAction::Transfer,
+            ChainAction::DeployContract,
+            ChainAction::CallContract,
+            ChainAction::UploadContractCode,
+        ] {
+            assert_eq!(
+                subsidy_basis_points(HardwareTier::EmbeddedAI, action),
+                subsidy_basis_points(HardwareTier::EmbeddedArm, action),
+                "EmbeddedAI debe espejar el piso EmbeddedArm en {action:?}"
+            );
+        }
+    }
+
     #[test]
     fn ocafb_3_ultra_pays_full_fee_canonical() {
         // Ultra: no subsidy except Read