change(chain): Split subsidy constants into submodules (ZcashFoundation#10185)

* Refactor subsidy constants into dedicated modules

* Use qualified names instead of name suffixes

* Restrict subsidy constants modules to crate visibility

---------

Co-authored-by: Alfredo Garcia <oxarbitrage@gmail.com>

Author: upbqdn

zebra-chain/CHANGELOG.md

@@ -5,6 +5,16 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+
+- `parameters::network::subsidy::constants` module.
+
+### Removed
+
+- All constants from `parameters::network::subsidy`.
+
 ## [4.0.0] - 2026-01-21
 
 ### Breaking Changes

zebra-chain/src/parameters/network.rs

@@ -294,9 +294,11 @@ impl Network {
         };
 
         match self {
-            Self::Mainnet => subsidy::EXPECTED_NU6_1_LOCKBOX_DISBURSEMENTS_TOTAL_MAINNET,
+            Self::Mainnet => {
+                subsidy::constants::mainnet::EXPECTED_NU6_1_LOCKBOX_DISBURSEMENTS_TOTAL
+            }
             Self::Testnet(params) if params.is_default_testnet() => {
-                subsidy::EXPECTED_NU6_1_LOCKBOX_DISBURSEMENTS_TOTAL_TESTNET
+                subsidy::constants::testnet::EXPECTED_NU6_1_LOCKBOX_DISBURSEMENTS_TOTAL
             }
             Self::Testnet(params) => params.lockbox_disbursement_total_amount(),
         }
@@ -312,9 +314,9 @@ impl Network {
         };
 
         let expected_lockbox_disbursements = match self {
-            Self::Mainnet => subsidy::NU6_1_LOCKBOX_DISBURSEMENTS_MAINNET.to_vec(),
+            Self::Mainnet => subsidy::constants::mainnet::NU6_1_LOCKBOX_DISBURSEMENTS.to_vec(),
             Self::Testnet(params) if params.is_default_testnet() => {
-                subsidy::NU6_1_LOCKBOX_DISBURSEMENTS_TESTNET.to_vec()
+                subsidy::constants::testnet::NU6_1_LOCKBOX_DISBURSEMENTS.to_vec()
             }
             Self::Testnet(params) => return params.lockbox_disbursements(),
         };