feat(session): Phase 1.5 — Session rotation 4h epochs canonical v0.0.7

Origin Chain runtime canonical ahora emite SessionEvent::NewSession cada 4
horas exactas per CHN-1 ratified. Substrate de rotation canonical establecido
para Phase 2 NPoS heredarlo sin breakage.

## Pallet añadido (per SBS-4)
- Index 6 Session (pallet_session 40.0.1) — validator session rotation per
  CHN-1 4h epochs. Phase 1 PoA preserves genesis validators canonical across
  rotations (SessionManager ()). Phase 2 NPoS introducira pallet_staking como
  SessionManager para rotation real per nominator stake + Pi 5 hardware tier
  weight.

## Configs canonical pallet_session
- SessionPeriod = BLOCK_HASH_COUNT (2400 bloques × 6s = 14400s = 4h exactas)
- SessionOffset = 0 (sesiones start at block 0)
- ValidatorId = ChainAccountId
- ValidatorIdOf = AccountIdIsValidatorId (custom identity converter Phase 1 PoA)
- ShouldEndSession/NextSessionRotation = PeriodicSessions<SessionPeriod, SessionOffset>
- SessionManager = () (preserves genesis Phase 1 PoA)
- SessionHandler = <opaque::SessionKeys as OpaqueKeys>::KeyTypeIdProviders
- Keys = opaque::SessionKeys (aura sr25519 + grandpa Ed25519)
- DisablingStrategy = () (Phase 2 NPoS introduce real slashing-based disable)

## Custom converter canonical
AccountIdIsValidatorId struct nueva — identity mapping AccountId → ValidatorId
Phase 1 PoA trivial. Phase 2 NPoS reemplazara con pallet_staking::StashOf<Self>
para real Stash/Controller separation canonical.

## Filosofía canonical
SessionPeriod = 4h es la frontera temporal canonical: cada 4h el chain
reflexiona on-chain quienes son los validators activos. Esta cadencia
institucional canonical es la minima necesaria para que Phase 2 NPoS pueda
evolucionar el set sin re-launching genesis. David canon 2026-05-14
materializado temporalmente.

## Build + tests
- cargo check 1.63s warm cache (pallet_session incremental)
- cargo build --release 7.70s warm cache clean
- ~57 tests passing (count preserved — session tests Phase 1.7 chain_spec)

## Decision empirica
pallet_session::Config::DisablingStrategy es nuevo stable2512 canonical (no
estaba en versiones anteriores). Phase 1 PoA: () preserva behavior original.
Phase 2 NPoS: UpToLimitWithReEnablingDisablingStrategy per CHN-3.

## Phase 1 progress
1.1 ✅ + 1.2 ✅ + 1.3 ✅ + 1.4 ✅ + 1.5 ✅ (esta). Next: 1.6 pallet_identity
Ed25519 DID + origin-chain-node real service.

7 pallets composed canonical:
- 0 System + 1 Timestamp + 2 Balances + 3 TransactionPayment
- 4 Aura + 5 Grandpa + 6 Session ← NEW
- Opaque SessionKeys consumed by pallet_session::Config::Keys ← NEW WIRE

Refs: CHARON_ROADMAP_V1 Phase 1.5, CHN-1 4h epoch rotation canonical, SBS-4
extended, arkhe-origin-chain commit pending

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,110 @@ by [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). Versions follow
 
 ## [Unreleased]
 
+## [0.0.7] — 2026-05-20 — Phase 1.5 "Session rotation canonical (4h epochs)"
+
+Charon sesión 1 continuación. **Session pallet canonical integrado** — Origin
+Chain runtime canonical ahora emite `SessionEvent::NewSession` cada 4 horas
+exactas per CHN-1 ratified canonical. Substrate de rotation canonical
+establecido para Phase 2 NPoS heredarlo sin breakage.
+
+### Pallet añadido canonical (per SBS-4)
+
+- **Index 6** `Session` (`pallet_session 40.0.1`) — **validator session
+  rotation canonical** per CHN-1 4h epochs. Phase 1 PoA preserves genesis
+  validators canonical across rotations (SessionManager `()`). Phase 2 NPoS
+  introduce `pallet_staking` como SessionManager canonical para rotation real
+  per nominator stake + Pi 5 hardware tier weight.
+
+### Configs canonical pallet_session
+
+```rust
+parameter_types! {
+    /// 2400 bloques × 6s = 14400s = 4 horas exactas per CHN-1
+    pub const SessionPeriod: BlockNumber = BLOCK_HASH_COUNT;
+    pub const SessionOffset: BlockNumber = 0;
+}
+
+type RuntimeEvent = RuntimeEvent;
+type ValidatorId = ChainAccountId;
+type ValidatorIdOf = AccountIdIsValidatorId;  // identity Phase 1 PoA
+type ShouldEndSession = pallet_session::PeriodicSessions<SessionPeriod, SessionOffset>;
+type NextSessionRotation = pallet_session::PeriodicSessions<SessionPeriod, SessionOffset>;
+type SessionManager = ();                     // Phase 1 PoA preserves genesis
+type SessionHandler = <opaque::SessionKeys as OpaqueKeys>::KeyTypeIdProviders;
+type Keys = opaque::SessionKeys;              // aura sr25519 + grandpa Ed25519
+type DisablingStrategy = ();                  // Phase 2 NPoS introduce real
+type WeightInfo = pallet_session::weights::SubstrateWeight<Runtime>;
+```
+
+### Custom canonical converter
+
+`AccountIdIsValidatorId` struct nueva canonical (identity mapping AccountId →
+ValidatorId Phase 1 PoA trivial). Phase 2 NPoS reemplazará canonical con
+`pallet_staking::StashOf<Self>` para real Stash/Controller separation.
+
+### Filosofía canonical incorporada
+
+Doc cita CHN-1: *"Epoch rotation every 4 hours selecting 100-150 active
+validators from millions of Pi 5 nodes eligible"*. Materializa empíricamente:
+
+- **Phase 1 PoA** (este v0.0.7): 5-7 static validators canonical, pero
+  `SessionId` rotates cada 4h emitting `SessionEvent::NewSession` observable
+  on-chain → ritmo institucional canonical materializado desde block 0.
+- **Phase 2 NPoS** (futuro): `pallet_staking` swappea canonical como
+  SessionManager — selecting 100-150 validators canonical per nominator stake
+  + HardwareTier weight (Inmutable #16 + #37 enforced from Phase 2 launch).
+
+David canon 2026-05-14 *"la libertad infinita acota solo donde empieza la del
+otro"* — el SessionPeriod canonical es la frontera temporal canonical: cada
+4h, el chain canonical reflexiona on-chain quiénes son los validators
+canonical activos. Esta cadencia institucional canonical es la mínima
+necesaria para que NPoS pueda evolucionar el set canonical sin re-launching
+genesis.
+
+### Tour canonical de Origin Chain runtime composition (7 pallets)
+
+```
+┌────────────────────────────────────────────────────────────┐
+│  Origin Chain Runtime v0.0.7 — frame_support::runtime!     │
+├────────────────────────────────────────────────────────────┤
+│  Index 0  System              (foundational frame)         │
+│  Index 1  Timestamp           (block clock → Aura)         │
+│  Index 2  Balances            (OGC token CHN-2)            │
+│  Index 3  TransactionPayment  (gas baseline CHN-8)         │
+│  Index 4  Aura                (PoA block production CHN-1) │
+│  Index 5  Grandpa             (finality gadget CHN-1)      │
+│  Index 6  Session             (4h epoch rotation CHN-1)    │ ← NEW
+├────────────────────────────────────────────────────────────┤
+│  Opaque SessionKeys: aura (sr25519) + grandpa (Ed25519)    │
+│  → consumed canonical by pallet_session::Config::Keys      │ ← NEW WIRE
+└────────────────────────────────────────────────────────────┘
+```
+
+### Phase 1 progress canonical
+
+- ✅ **1.1** Scaffold (v0.0.2)
+- ✅ **1.2** Substrate foundation (v0.0.4)
+- ✅ **1.3** Pallets foundation (v0.0.5)
+- ✅ **1.4** Consensus PoA Aura+GRANDPA (v0.0.6)
+- ✅ **1.5** **Session rotation 4h epochs** (v0.0.7) ← **ESTA**
+- ⏳ **1.6** `pallet_identity` Ed25519 DID + `origin-chain-node` real service
+- ⏳ **1.7** Genesis `chain_spec.rs` BM V2 allocation (40/25/15/15/5)
+
+### Build canonical
+
+- `cargo check --workspace`: **1.63s** (warm cache, pallet_session incremental)
+- `cargo build --release`: **7.70s** (warm cache canonical)
+- Tests passing: **~57** (mismo count — session tests llegan Phase 1.7 cuando
+  chain_spec con validators reales se integre)
+
+### Decision empírica documentada
+
+`pallet_session::Config::DisablingStrategy` es nuevo en stable2512 canonical
+(no estaba en versiones anteriores). Phase 1 PoA: `()` canonical preserva
+behavior original. Phase 2 NPoS canonical: `UpToLimitWithReEnablingDisablingStrategy`
+para slashing-based validator disabling per CHN-3 ratified canonical.
+
 ## [0.0.6] — 2026-05-20 — Phase 1.4 "Consensus PoA canonical (Aura+GRANDPA)"
 
 Charon sesión 1 continuación. **Consensus PoA canonical activado** — Origin