chore: functional removal of cost-voting (2/2)

[cylewitruk-stacks]

Description

This PR fully removes the SIP-006's .cost-voting contract's functional side-effects.

This was contingent on SIP-044 ratification and mainnet Epoch 4.0 activation, both of which have now occurred.

• Supersedes: chore: remove cost voting r2 - full functional removal (post-4.0) #7342
• Follows: chore: remove cost voting r1 - epoch 4.0 disablement gate #7341 (1/2)

Applicable issues

• Part 2 of https://github.com/stx-labs/core-epics/issues/255 (subtask https://github.com/stx-labs/core-epics/issues/363)

Additional info (benefits, drawbacks, caveats)

• Removes a whole bunch of unused code/tests.
• The removal of is_cost_contract_eligible from ContractAnalysis is backwards-compatible as serde_json ignores unknown fields during deserialization of previously stored analyses.

Checklist

• SIP-044 ratified
• chore: remove cost voting r1 - epoch 4.0 disablement gate #7341 merged
• Epoch 4.0 mainnet activation
• Changelog fragment(s) or "no changelog" label added (see changelog.d/README.md)

[Copilot]

🟡 Changes recommended

Pre-4.0 replay compatibility and breaking API disclosure must be addressed.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Removes SIP-006 cost-voting side effects after Epoch 4.0.

Changes:

• Removes dynamic cost replacement and contract-call short-circuiting.
• Removes cost-contract eligibility analysis and related APIs.
• Deletes obsolete tests and adds an Epoch 4.0 native-cost check.

File summaries

File	Description
stackslib/src/clarity_vm/tests/costs.rs	Removes cost-voting tests; adds native-cost check.
stackslib/src/chainstate/stacks/boot/contract_tests.rs	Removes voting and arithmetic-only tests.
stacks-node/src/tests/neon_integrations.rs	Removes cost-voting integration test.
stacks-common/src/types/tests.rs	Removes epoch gate test.
stacks-common/src/types/mod.rs	Removes cost-voting support gate.
clarity/src/vm/functions/database.rs	Removes contract-call cost interception.
clarity/src/vm/costs/mod.rs	Removes voting-state loading and replacement logic.
clarity/src/vm/contexts.rs	Removes free-execution support.
clarity/src/vm/ast/mod.rs	Updates test cost tracker.
clarity/src/vm/analysis/types.rs	Removes eligibility metadata field.
clarity/src/vm/analysis/type_checker/v2_1/mod.rs	Updates cost tracker implementation.
clarity/src/vm/analysis/type_checker/v2_05/mod.rs	Updates cost tracker implementation.
clarity/src/vm/analysis/mod.rs	Removes arithmetic analysis pass.
clarity/src/vm/analysis/contract_interface_builder/mod.rs	Updates analysis destructuring.
clarity/src/vm/analysis/arithmetic_checker/tests.rs	Deletes checker tests.
clarity/src/vm/analysis/arithmetic_checker/mod.rs	Deletes arithmetic checker.
changelog.d/7342-cost-voting-functional-removal.removed	Adds removal notice.

Review details

• Files reviewed: 17/17 changed files
• Comments generated: 2
• Review effort level: Balanced

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[coveralls]

Coverage Report for CI Build 33595864648

Coverage decreased (-0.03%) to 86.406%

Details

• Coverage decreased (-0.03%) from the base build.
• Patch coverage: 6 uncovered changes across 1 file (23 of 29 lines covered, 79.31%).
• 230 coverage regressions across 32 files.

Uncovered Changes

File	Changed	Covered	%
clarity/src/vm/costs/mod.rs	25	19	76.0%
Total (2 files)	29	23	79.31%

Coverage Regressions

230 previously-covered lines in 32 files lost coverage.

Top 10 Files by Coverage Loss	Lines Losing Coverage	Coverage
clarity/src/vm/database/clarity_db.rs	58	79.41%
clarity/src/vm/mod.rs	17	88.97%
stackslib/src/clarity_vm/database/marf.rs	16	60.42%
stackslib/src/net/stackerdb/sync.rs	16	74.31%
clarity/src/vm/database/key_value_wrapper.rs	15	80.81%
stacks-signer/src/v0/signer_state.rs	14	92.54%
stackslib/src/net/download/nakamoto/download_state_machine.rs	9	89.74%
stackslib/src/net/download/nakamoto/tenure_downloader_unconfirmed.rs	9	74.13%
clarity/src/vm/tooling/mod.rs	8	75.76%
stackslib/src/net/relay.rs	8	74.93%

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Coverage Stats

Relevant Lines:	230198
Covered Lines:	198905
Line Coverage:	86.41%
Coverage Strength:	20246240.59 hits per line

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💛 - Coveralls

[brice-stacks]

lgtm!