Preserve configured senders across draft writes

[jr-lillard]

Summary

• expose the optional acting sender ID on draft content
• preserve an explicitly selected sender when creating, updating, and sending drafts
• add CreateReplyDraftWithSender while retaining the existing default-sender behavior for current callers
• cover create, update, send, and reply-draft sender propagation with focused tests

Testing

• mise exec -- make check
• go test -race -count=1 ./...
• GOTOOLCHAIN=go1.26.6 govulncheck ./...

---

Summary by cubic

Preserves an explicitly selected sender across draft create, update, send, and reply-draft flows, instead of always falling back to the identity's default sender.

• Adds ActingSenderID to DraftContent for message drafts; zero keeps the default-sender behavior.
• Adds CreateReplyDraftWithSender for reply drafts while existing callers keep using the default sender.
• Rejects negative acting sender IDs with a usage error on draft writes.

Looks good!

^{Written for commit baa9c85. Summary will update on new commits.}

[Copilot]

Pull request overview

Adds explicit sender preservation to draft creation, updates, sending, and reply drafts.

Changes:

• Adds ActingSenderID to draft content.
• Adds CreateReplyDraftWithSender.
• Adds focused sender propagation tests.

Tip

If you aren't ready for review, convert to a draft PR.
Click "Convert to draft" or run gh pr ready --undo.
Click "Ready for review" or run gh pr ready to reengage.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
go/pkg/hey/messages.go	Propagates explicitly selected senders through draft writes.
go/pkg/hey/entries.go	Adds sender-aware reply draft creation.
go/pkg/hey/drafts_test.go	Tests explicit sender propagation and validation.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[jeremy]

Thanks for this, and apologies that it sat while the same problem was being fixed from another direction. The shape you proposed has landed on main through #135 (released in v0.29.0): DraftContent carries ActingSenderID, Messages().CreateDraft, UpdateDraft and SendDraft resend it on every revision, Entries().CreateReplyDraft and CreateReply take the acting sender as a parameter, and resolveActingSenderID validates the ID against the identity's senders rather than accepting any positive integer.

That leaves nothing in this branch that main lacks, so I'm marking it superseded rather than asking for a rebase. The CLI half, choosing a sender when composing, is tracked in basecamp/hey-cli#353 and now has the SDK support it needs.