Use GetLedgerRaw in getLatestLedger endpoint

[cjonas9]

What

Uses the new raw-bytes patterning used in getLedger in getLatestLedger:

• Add GetLedgerRaw(ctx, sequence) ([]byte, xdr.LedgerHeaderHistoryEntry, bool, error) to LedgerReader
  • Returns raw bytes of ledger meta, the header, and whether it was found/if the request error'd
• Updates the getLatestLedger handler to call GetLedgerRaw
• Updates mocks/tests with GetLedgerRaw

Why

getLatestLedger currently wastes time calling GetLedgers to get a single LedgerCloseMeta, which causes an Unmarshal to XDR. The handler then marshals this XDR to binary. On each call, we pay for a ~2.8Mb Unmarshal and Marshal that can be completely bypassed.

Known limitations

N/A

[Copilot]

Pull request overview

Optimizes getLatestLedger by returning stored ledger metadata bytes directly, avoiding unnecessary XDR round-trips.

Changes:

• Adds GetLedgerRaw to ledger readers and mocks.
• Reuses raw header parsing in database reads.
• Updates the endpoint and tests for raw metadata.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
cmd/stellar-rpc/internal/db/ledger.go	Adds raw ledger retrieval and header parsing.
cmd/stellar-rpc/internal/db/mocks.go	Implements raw retrieval in the database mock.
cmd/stellar-rpc/internal/methods/get_latest_ledger.go	Builds responses from raw metadata and parsed headers.
cmd/stellar-rpc/internal/methods/get_latest_ledger_test.go	Updates test reader behavior for raw metadata.
cmd/stellar-rpc/internal/methods/mocks.go	Extends the methods mock with GetLedgerRaw.

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