feat(fees): v0.0.20 pallet-origin-fees scaffold trait-first + vendor OitFeeSchedule Mathi (OCAFB-1..6)

Phase 2.4 FEES pallet scaffold canonical pattern análogo Phase 2.1 (scaffold →
wired → impl → Runtime API). New crate `origin-chain-fees` con vendor copy
Mathi OitFeeSchedule trait + matrices + Mock desde commit ce4fafb (536 LOC).

## Cross-pillar source-of-truth canonical

NEW canonical: `origin-chain-types::actions::ChainAction` (OCAFB-2). Mathi
local mirror puede swap post-OCAFB ratify 7/7 (deadline 2026-06-21).
NEW canonical: `origin-chain-types::tiers::SubscriptionTier` (mirror Mathi).

## Surface canonical scaffold v0.0.20

- Pallet<T> + Config trait + RuntimeEvent
- AccountFees<StorageMap<AccountId, FeeHistory>> per-account history
- FeeHistory { total_paid, action_count } aggregate stats
- Events FeeCharged + FeeRefunded + EntitlementBlocked
- Errors InsufficientBalance + EntitlementLocked + FeeOverflow + AccountNotFound
- FeeRejectionReason enum (mirror PROV pattern Phase 2.1)
- Scaffold dispatchable compute_fee_for_action (placeholder event v0.0.20 → real v0.0.22)

## Vendor copy OitFeeSchedule canonical

- OitFeeSchedule trait 4-method dyn-compatible Send + Sync (OCAFB-1)
- subsidy_basis_points const fn matrix Inmutable #16 anti-clasista (OCAFB-3)
- entitlement_unlocked const fn matrix Inmutables #37 + #18 (OCAFB-4)
- compute_fee formula 3-step (OCAFB-5)
- OitFeeScheduleMock builder pattern (OCAFB-6)
- arc_mock() helper canonical Arc<dyn OitFeeSchedule>

## Files canonical

- NEW: crates/origin-chain-fees/Cargo.toml (mirror provenance pattern)
- NEW: crates/origin-chain-fees/src/lib.rs (~250 LOC pallet scaffold)
- NEW: crates/origin-chain-fees/src/fee_schedule.rs (~400 LOC vendor copy)
- NEW: crates/origin-chain-types/src/actions.rs (~130 LOC ChainAction canonical)
- EDIT: crates/origin-chain-types/src/tiers.rs (SubscriptionTier added)
- EDIT: crates/origin-chain-types/src/lib.rs (mod actions + re-exports)
- EDIT: Cargo.toml (workspace member origin-chain-fees)
- EDIT: CHANGELOG.md (v0.0.20 entry pattern Phase 2.1)

## Verification

- cargo build -p origin-chain-fees 1.83s clean
- cargo test -p origin-chain-fees — 20 tests verde, 0 failures
  (16 vendor + 4 pallet scaffold)
- cargo test -p origin-chain-types — 55 tests passing (+8 nuevos)
  (6 ChainAction + 2 SubscriptionTier)
- Zero workspace compile errors

🚀 Phase 2.4 scaffold canonical ready. Wire pattern v0.0.21 next.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Cargo.lock

@@ -2177,6 +2177,21 @@ dependencies = [
  "origin-chain-types",
 ]
 
+[[package]]
+name = "origin-chain-fees"
+version = "0.0.1"
+dependencies = [
+ "frame-support",
+ "frame-system",
+ "origin-chain-types",
+ "parity-scale-codec",
+ "scale-info",
+ "sp-api",
+ "sp-core",
+ "sp-io",
+ "sp-runtime",
+]
+
 [[package]]
 name = "origin-chain-governance"
 version = "0.0.1"