fix(dpp): return UnsupportedFeatureError for legacy state transition structure validation

[QuantumExplorer]

Issue being fixed or feature implemented:

Structure validation for legacy/identity-based state transitions was returning an empty success result, which obscured the fact that no actual validation was being performed. This made it unclear
whether validation passed because the transition was valid or because validation wasn't implemented.

What was done:

1. rs-dpp/state_transition/mod.rs: Changed validate_structure for legacy state transitions (DataContractCreate, DataContractUpdate, Batch, IdentityCreate, IdentityTopUp, IdentityCreditWithdrawal,
   IdentityUpdate, IdentityCreditTransfer, MasternodeVote) to return UnsupportedFeatureError instead of an empty validation result. This explicitly signals that client-side structure validation is
   not implemented for these transition types.
2. rs-sdk/transition/validation.rs: Updated ensure_valid_state_transition_structure to allow UnsupportedFeatureError to pass through without blocking broadcast. This allows legacy state
   transitions to still be broadcast while address-based transitions get proper structure validation with real error reporting.

The platform still performs full validation during execution, so this change only affects client-side pre-broadcast checks.

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have added "!" to the title and described breaking changes in the corresponding section if my code contains any
• I have made corresponding changes to the documentation if needed

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/dontAssumeStructureValidation

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[github-actions]

✅ gRPC Query Coverage Report

================================================================================
gRPC Query Coverage Report - NEW QUERIES ONLY
================================================================================

Total queries in proto: 49
Previously known queries: 47
New queries found: 2

================================================================================

New Query Implementation Status:
--------------------------------------------------------------------------------
✓ getAddressInfo                                /home/runner/work/platform/platform/packages/rs-sdk/src/platform/query.rs
✓ getAddressesInfos                             /home/runner/work/platform/platform/packages/rs-sdk/src/platform/fetch_many.rs

================================================================================
Summary:
--------------------------------------------------------------------------------
New queries implemented: 2 (100.0%)
New queries missing: 0 (0.0%)

Total known queries: 49
  - Implemented: 46
  - Not implemented: 2
  - Excluded: 1

Not implemented queries:
  - getConsensusParams
  - getTokenPreProgrammedDistributions

[github-actions]

✅ DashSDKFFI.xcframework built for this PR.

• Workflow run: https://github.com/dashpay/platform/actions/runs/20117177857
• Artifacts: DashSDKFFI.xcframework (folder), DashSDKFFI.xcframework.zip, xc_checksum.txt

SwiftPM (host the zip at a stable URL, then use):

.binaryTarget(
  name: "DashSDKFFI",
  url: "https://your.cdn.example/DashSDKFFI.xcframework.zip",
  checksum: "feadd17bf77ce1af91bbf7f826b9c2b3e580f95e99ae3b7a31d0c885e416341f"
)

Xcode manual integration:

• Download 'DashSDKFFI.xcframework' artifact from the run link above.
• Drag it into your app target (Frameworks, Libraries & Embedded Content) and set Embed & Sign.
• If using the Swift wrapper package, point its binaryTarget to the xcframework location or add the package and place the xcframework at the expected path.

[lklimek]

Maybe

Suggested change

	) -> crate::validation::SimpleConsensusValidationResult {
	) -> ConsensusValidationResult<bool> {

where bool:

• true - correct
• false - undecided

[QuantumExplorer]

This is outside the normal pattern and confusing. The validation result would pass, but the bool would say it's valid? It's three tiers and hurts my brain.

[QuantumExplorer]

I'm going to merge this in for now, soonish we will move structure validation from drive-abci to dpp.