chore: remove cost voting r1 - epoch 4.0 disablement gate

[cylewitruk-stacks]

This PR disables the SIP-006's .cost-voting contract's side-effects starting from epoch 4.0 as proposed in SIP-044.

Most of the code additions here are tests and related; and most will get axed in r2.

Description

Applicable issues

• Part 1 of https://github.com/stx-labs/core-epics/issues/255 (subtask https://github.com/stx-labs/core-epics/issues/362)

Additional info (benefits, drawbacks, caveats)

• The cost upgrade/voting function has never successfully been used in mainnet. Once disabled, the cost tracker skips applying .cost-voting state entirely and resolves all cost functions through the node's latest initialized boot cost contract (based on its current epoch). For epoch 4.0, this is the .costs-5 contract.
• Added additional test coverage proving the effects of .cost-voting before and after epoch 4.0.
• Minor test-only refactor adding Range syntax support and a couple of helpers for StacksEpochId.
• initialize_epoch_4_0() requires .sbtc-token and .sbtc-registry, so I split out a boot-contract initialization helper and epoch 4.0 cost-contract initialization helper (which initialize_epoch_4_0() now calls -- future refactor potential for remaining initialization functions).

Checklist

• Test coverage for new or modified code paths
• For new Clarity features or consensus changes, add property tests (see docs/property-testing.md)
• Changelog fragment(s) or "no changelog" label added (see changelog.d/README.md)

[Copilot]

Pull request overview

This PR retires SIP-006 .cost-voting side effects starting at epoch 4.0 (per SIP-044), so the cost tracker ignores .cost-voting state at/after epoch 4.0 and resolves cost functions exclusively via the epoch’s boot cost contract (e.g. .costs-5 in 4.0).

Changes:

• Gate cost-voting state loading in the Clarity cost tracker so it is ignored for epoch >= 4.0.
• Add/refactor cost-voting integration tests to assert behavior before epoch 4.0 and after epoch 4.0, plus test harness helpers for epoch bootstrapping.
• Introduce a test-only StacksEpochId range helper trait to simplify epoch-range iteration in tests and update existing tests to use Rust range syntax.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
stackslib/src/net/api/tests/postblock_v3.rs	Removes an unused Clarity hash import from API tests.
stackslib/src/clarity_vm/tests/costs.rs	Refactors epoch setup for cost tests and adds assertions for pre/post epoch-4.0 cost-voting behavior.
stackslib/src/clarity_vm/clarity.rs	Adds boot-contract instantiation helpers and exposes an epoch-4.0 cost-contract-only initializer for tests.
stackslib/src/chainstate/tests/runtime_tests.rs	Switches test epoch ranges to use the new range extension helper.
stackslib/src/chainstate/tests/runtime_analysis_tests.rs	Switches test epoch ranges to use the new range extension helper.
stackslib/src/chainstate/tests/consensus.rs	Updates epoch range handling in tests and adjusts doc comment to match new range usage.
stackslib/src/chainstate/tests/consensus_unit_tests.rs	Switches test epoch ranges to use the new range extension helper.
stacks-common/src/types/tests.rs	Adds tests for the epoch-4.0 cost-voting gate and the new epoch range extension behavior.
stacks-common/src/types/mod.rs	Adds supports_cost_voting_contract() and introduces a test-only epoch range extension trait + helpers.
clarity/src/vm/tests/epoch_gating.rs	Updates epoch gating test to use the new range-based helper.
clarity/src/vm/costs/mod.rs	Skips loading .cost-voting state at/after epoch 4.0 and falls back to boot defaults.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[cylewitruk-stacks]

Whoops, think I forgot the .added tail on the changelog file -- will fix that when I switch back from the r2 branch.

[coveralls]

Coverage Report for CI Build 27958144415

Coverage increased (+0.2%) to 86.195%

Details

• Coverage increased (+0.2%) from the base build.
• Patch coverage: 18 uncovered changes across 3 files (93 of 111 lines covered, 83.78%).
• 8107 coverage regressions across 119 files.

Uncovered Changes

File	Changed	Covered	%
clarity/src/vm/costs/mod.rs	11	4	36.36%
stacks-common/src/types/mod.rs	29	23	79.31%
stackslib/src/clarity_vm/clarity.rs	71	66	92.96%

Coverage Regressions

8107 previously-covered lines in 119 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
stackslib/src/chainstate/burn/db/sortdb.rs	580	90.27%
stackslib/src/config/mod.rs	440	69.41%
stackslib/src/chainstate/nakamoto/mod.rs	404	84.76%
stackslib/src/net/mod.rs	310	78.15%
clarity/src/vm/database/clarity_db.rs	273	82.02%
stackslib/src/chainstate/stacks/db/transactions.rs	269	97.03%
stackslib/src/chainstate/stacks/index/storage.rs	263	82.41%
clarity/src/vm/database/structures.rs	253	77.25%
stackslib/src/chainstate/stacks/boot/mod.rs	246	94.28%
stackslib/src/chainstate/stacks/miner.rs	222	83.18%

---

Coverage Stats

Relevant Lines:	228642
Covered Lines:	197077
Line Coverage:	86.19%
Coverage Strength:	18583957.98 hits per line

---

💛 - Coveralls

[brice-stacks]

lgtm! 95% refactoring and code cleanup and 5% disabling cost-voting 😅

[github-actions]

Closed PR has been locked after 14 days of inactivity.