Fix SetOpSourceAccount silently ignoring invalid source account errors

[tamirms]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've reviewed the changes in this PR and if I consider them worthwhile for being mentioned on release notes then I have updated the relevant CHANGELOG.md within the component folder structure. For example, if I changed horizon, then I updated (services/horizon/CHANGELOG.md. I add a new line item describing the change and reference to this PR. If I don't update a CHANGELOG, I acknowledge this PR's change may not be mentioned in future release notes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

SetOpSourceAccount was discarding the error returned by MuxedAccount.SetAddress, which could produce a partially initialized MuxedAccount that panics on subsequent Address() calls. Return the error instead and check it in all 27 BuildXDR callers.

Known limitations

[N/A]

[Copilot]

Pull request overview

This PR fixes txnbuild.SetOpSourceAccount silently discarding invalid muxed/G-address errors by returning an error from SetAddress and propagating it through all BuildXDR() call sites, preventing partially-initialized xdr.MuxedAccount values that can later panic.

Changes:

• Change SetOpSourceAccount to return an error and wrap invalid address failures.
• Update all affected BuildXDR() implementations to handle and return SetOpSourceAccount errors.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
txnbuild/operation.go	Make SetOpSourceAccount return errors instead of silently ignoring invalid source accounts.
txnbuild/account_merge.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/allow_trust.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/begin_sponsoring_future_reserves.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/bump_sequence.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/change_trust.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/claim_claimable_balance.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/clawback.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/clawback_claimable_balance.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/create_account.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/create_claimable_balance.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/create_passive_offer.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/end_sponsoring_future_reserves.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/extend_footprint_ttl.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/inflation.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/invoke_host_function.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/liquidity_pool_deposit.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/liquidity_pool_withdraw.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/manage_buy_offer.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/manage_data.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/manage_offer.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/path_payment.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/path_payment_strict_send.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/payment.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/restore_footprint.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/revoke_sponsorship.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/set_options.go	Propagate SetOpSourceAccount error in BuildXDR().
txnbuild/set_trust_line_flags.go	Propagate SetOpSourceAccount error in BuildXDR().

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[Copilot]

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated no new comments.

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