build: NONEVM-4285: implement stellar encoder

[FelixFan1992]

1. implement encoder for Stellar
2. set up dependabot
3. Stellar MCMS currently uses ABI encoding for merkle roots. the full implementation is here

[changeset-bot]

🦋 Changeset detected

Latest commit: 7f05103

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@smartcontractkit/mcms	Patch

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[gustavogama-cll]

another nit: if you use n.SetString(*af.Value, 0) it auto-detects the 0x prefix and interprets it as hex.

[gustavogama-cll]

Added a few minor suggestions about small optimizations which can be safely ignored. The only real requests I have is (1) to review the functions that are initially exported (remember we can always change from private to public afterwards); (2) improve the test coverage, for this type of code I think we should aim for >80%.

[Copilot]

Pull request overview

This PR introduces Stellar (Soroban MCMS) ABI-compatible hashing/encoding support in the Go SDK and updates dependency management to track the new Stellar SDK dependency.

Changes:

• Add Stellar as a supported chain family in chain selector handling.
• Introduce a new sdk/stellar package implementing sdk.Encoder plus ABI preimage construction and golden-vector tests.
• Update go.mod/go.sum, Dependabot allowlist, and add a changeset for publishing.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
types/chain_selector.go	Adds chainsel.FamilyStellar to the list of supported families.
sdk/stellar/encoder.go	Implements sdk.Encoder for Stellar and parses optional additionalFields.value.
sdk/stellar/encode.go	Implements Stellar-specific ABI word packing and Keccak hashing for metadata/ops.
sdk/stellar/constants.go	Defines ABI/layout constants and domain separators.
sdk/stellar/address.go	Parses Stellar contract identifiers from strkey or 32-byte hex.
sdk/stellar/chain.go	Maps chain selector → Stellar network ID via chain-selectors.
sdk/stellar/encoder_test.go	Tests encoder output consistency and contract-id parsing.
sdk/stellar/encode_test.go	Tests domain constants and hashing against golden vectors / ABI encoder.
go.mod	Adds github.com/stellar/go-stellar-sdk (and indirect go-xdr).
go.sum	Updates dependency checksums (incl. Stellar deps, go-errors bump).
.github/dependabot.yml	Allowlists github.com/stellar/go-stellar-sdk for gomod updates.
.changeset/free-peaches-itch.md	Declares a patch release for Stellar encoder support.

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[cl-sonarqube-production]

Quality Gate passed

Issues
13 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
92.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube