core/validatorapi: add payload attestation endpoints

[KaloyanTanev]

Add the VC-facing payload attestation surface: GET /eth/v1/validator/payload_attestation_data served from the DutyDB via AwaitPayloadAttestationData, and POST /eth/v1/beacon/pool/payload_attestations as partial-signature intake (validator index to cluster pubkey mapping, partial signature verification under DOMAIN_PTC_ATTESTER, grouped by slot). The required Eth-Consensus-Version request header is enforced on submission. Also wires DutyPayloadAttestation into the bcast delay metric (measured from the duty trigger, consistent with other duties), duty deadline, and core.Wire/tracing plumbing.

Handler methods are plain (not eth2client interfaces) until go-eth2-client exposes the PTC provider interfaces (attestantio/go-eth2-client#311); the 204 no-block-seen semantics land with the fetcher PR.

category: feature
ticket: #4324

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

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

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

This PR adds validator-client-facing support for Gloas/ePBS Payload Timeliness Committee (PTC) payload attestations to Charon’s core/validatorapi, exposing a new data-fetch endpoint backed by DutyDB.AwaitPayloadAttestationData and a new submission endpoint for partially signed payload attestation messages, while wiring the new duty type into deadline handling, broadcast delay metrics, and tracing.

Changes:

• Add GET /eth/v1/validator/payload_attestation_data returning gloas.PayloadAttestationData (with Eth-Consensus-Version: gloas response header).
• Add POST /eth/v1/beacon/pool/payload_attestations to ingest partial payload attestation signatures, enforce Eth-Consensus-Version: gloas, and dispatch grouped partials downstream.
• Wire DutyPayloadAttestation into deadlines, bcast delay metric selection, and tracing/wiring plumbing; update docs and tests accordingly.

Reviewed changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
docs/architecture.md	Documents the new DutyPayloadAttestation duty type in the architecture overview.
core/validatorapi/validatorapi.go	Adds component hooks for awaiting payload attestation data and submitting payload attestation messages with partial signature verification and slot-grouping.
core/validatorapi/validatorapi_test.go	Adds unit tests for the new component methods (data retrieval + submission path).
core/validatorapi/router.go	Adds the new GET/POST routes and enforces Eth-Consensus-Version: gloas on submission.
core/validatorapi/router_internal_test.go	Adds route-level tests for the new endpoints, including bad/missing version header behavior.
core/validatorapi/mocks/handler.go	Regenerates the Handler mock to include the new handler methods.
core/tracing.go	Wraps DutyDBAwaitPayloadAttestation with tracing spans.
core/interfaces.go	Extends core interfaces/wiring to include AwaitPayloadAttestationData registration and wiring glue.
core/deadline.go	Adds a DutyPayloadAttestation deadline duration of one slot.
core/bcast/bcast.go	Includes DutyPayloadAttestation in the delay-metric offset selection set.

Files not reviewed (1)

• core/validatorapi/mocks/handler.go: Generated file

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[codecov]

Codecov Report

❌ Patch coverage is 70.58824% with 30 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (gloas@563c58c). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
core/validatorapi/validatorapi.go	71.42%	6 Missing and 6 partials ⚠️
core/validatorapi/router.go	83.67%	4 Missing and 4 partials ⚠️
core/tracing.go	0.00%	5 Missing ⚠️
core/interfaces.go	0.00%	3 Missing ⚠️
core/deadline.go	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             gloas    #4657   +/-   ##
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  Coverage         ?   58.81%           
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  Files            ?      245           
  Lines            ?    34296           
  Branches         ?        0           
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  Hits             ?    20171           
  Misses           ?    11621           
  Partials         ?     2504           

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