…er Migration

- Add DParameterProvider trait for mockable D Parameter sourcing
- Implement MockDParameterProvider (uses inherent data for backward compat)
- Implement FixedDParameterProvider for testing
- Update select_authorities to use select_authorities_with_provider
- Remove DParameterOverride storage and override_d_parameter extrinsic
- Update pc-chain-config.json with new Aiken policy IDs:
  - node-dev-01: 51f812332ccc276d1dfa9da923c2235b91a5150ff275b633a5fa1bdb
  - qa-net: 6c327f1fe5e3b2619c62ca642892146c7326a91dc47f6006f6cdf690
  - preview: 4057188de00d74c6679263989745309f02bf55f8806061943124489b
  - preprod: 369ee95be4c68a2984733a8c727ecd28df3039a3e5f1e80290b08eec
- Add test plan document

WP: Aiken Permissioned Candidates & D Parameter Migration
Ticket: PM-20994

- Change manual tests from ✅ to ⬜ (Not Started)
- Add ⬜ Not Started to legend
- Add Notes column to test matrix
- Add detailed Manual Verification Procedures section
- Include code review checklists for TC-0004-04/05/07

TC-0004-04 and TC-0004-05 are compile-time + code review only,
not unit tests. Changed Unit Test column from ✅ to ➖ (N/A).

- TC-0004-04/05: Now 'verified by compilation' (not manual review)
- TC-0004-07: Removed (config file content verified at dev time)
- Removed Manual Verification Procedures for code review items

- Renumber tests sequentially (TC-01 through TC-06)
- Remove compile-time verification entries (not tests)
- Remove config file verification (dev-time check)
- Remove future test cases section
- Simplify test matrix (unit tests only)
- Streamline test case descriptions

Document the migration from Haskell to Aiken Permissioned Candidates
contracts and the D Parameter provider abstraction.

WP: Aiken Permissioned Candidates Migration

The struct is only used in unit tests, not in runtime-benchmarks.
Restricting to #[cfg(test)] fixes dead_code warning when building
with --features runtime-benchmarks.

- Replace Good/Bad/Neutral format with flattened ✅/❌ icon list
- Remove Implementation Approach section (design work, not decision)
- Remove Technical Details section (policy IDs are implementation details)
- Consolidate structure: Decision Drivers → Options → Decision → Consequences
- Add proper Confirmation section with validation criteria

ADRs document decisions, not design.

- docs/decisions/0005-aiken-permissioned-candidates-d-parameter-migration.md -> docs/decisions/adr-aiken-permissioned-candidates-d-parameter-migration.md
- docs/tests/0005-aiken-permissioned-candidates-d-parameter-migration.md -> docs/tests/test-plan-aiken-permissioned-candidates-d-parameter-migration.md
- Add ADR: prefix to title

- Remove d_parameter.rs module (trait abstraction no longer needed)
- D Parameter now sourced directly from SystemParameters::get_d_parameter()
- Update ADR status to Accepted
- Update test plan to reflect pallet integration

Depends-on: PR #387

- Add PR link to header
- Use PR378-TC-## format for Test IDs with hyperlinks to source
- Add column width divs to table
- Hyperlink symbols in Overview to source definitions
- Use proper   <br> format for multi-step entries

Add new RPC endpoint that returns Ariadne parameters with D Parameter
sourced from pallet-system-parameters instead of Cardano contracts.

Changes:
- Add MidnightAriadneRpc module in node/src/ariadne_rpc.rs
- Compose with SessionValidatorManagementQuery for candidate data
- Override D Parameter with pallet-sourced value
- Add 11 unit tests covering mock API, serialization, and override logic
- Update UI config with new endpoint definition
- Mark deprecated flag on old sidechain_getAriadneParameters endpoint
- Update ADR with RPC migration notes

The new endpoint midnight_getAriadneParameters provides the authoritative
D Parameter value while maintaining backward-compatible response schema.

Add E2E test coverage for pallet-system-parameters RPC endpoints:
- verify_system_parameters_genesis_via_rpc: validates genesis values
- verify_system_parameters_response_format: checks camelCase format
- query_system_parameters_at_historical_block: tests historical queries

Add MidnightClient helper methods for system parameters RPC:
- get_terms_and_conditions / get_terms_and_conditions_at
- get_d_parameter / get_d_parameter_at
- get_best_block_hash / wait_for_next_finalized_block

Ref: PM-20991

Change TermsAndConditionsRpcResponse.hash from String to H256 for
improved type safety. The JSON wire format remains unchanged as H256
serializes to the same hex string format (0x-prefixed).

- pallet-system-parameters: remove unused 'log' dep, ignore 'serde' (used by frame_support macros)
- pallet-system-parameters-rpc: remove unused 'hex' dep (no longer needed after H256 refactor)
- midnight-primitives-system-parameters: remove unused parity-scale-codec, scale-info, sp-runtime, sp-core

…into feat/aiken-permissioned-candidates-migration

Remove T&C-related additions from e2e tests that were out of scope
for the Aiken permissioned candidates migration work package:

- Remove TermsAndConditionsResponse struct from midnight.rs
- Remove get_terms_and_conditions and get_terms_and_conditions_at methods
- Remove T&C constants and assertions from e2e tests
- Rename tests to focus on D Parameter verification only

D Parameter RPC tests remain as they are in scope for this migration.