test(adkrest/models): add EventActions field mapping coverage - #726

Apologies for the long silence here — you made the change I asked for back in June and this then sat for far too long. I've re-validated it against current main rather than the base it was written on, and it holds up.

It still works after the drift. Your branch is 123 commits behind, so I rebased it locally onto 53a0bc0 and ran it there: clean rebase with no conflict, go build ./... and the package suite both green, five tests passing — your three alongside the two that landed on main in the meantime.

It still pins real behaviour. I broke the mapping code nine different ways and re-ran the package suite twice for each, once with your file and once without. All nine fail with your file and pass without it, so every one is coverage main does not have today. The nicest of them is the Escalate/SkipSummarization source swap: your "all fields populated" case sets both to true and your "zero value" case sets both to false, so neither can see a swap — it is caught only because you also wrote the isolated single-field cases. Those cases look redundant next to the combined one, which is exactly why they usually get dropped.

No overlap with what landed since. event_test.go grew while this was waiting, but it covers RequestedToolConfirmations, Compaction and the workflow fields. Yours covers TransferToAgent, Escalate, SkipSummarization, StateDelta and ArtifactDelta. The two files are disjoint.

One thing worth knowing, since it changes the reasoning behind the wording fix rather than the fix itself. When I raised RequestedToolConfirmations in June it genuinely was not carried by the REST model. It is now, in both directions, and main has since added a seventh field, Compaction, which is deliberately outbound-only — FromSessionEvent maps it and ToSessionEvent drops it, so a client cannot erase conversation history and speak into the gap. Your hedged "the mapped EventActions fields" is still accurate, just for a different reason than when you wrote it.

That does leave one sharp edge in TestFromSessionEvent_RoundTrip. Its comment says the event round-trips "without losing any mapped EventActions fields", and Compaction is a mapped field that intentionally does not survive the trip. If someone later adds Compaction to that fixture to make the test match its own comment, the failure they get reads like data loss in ToSessionEvent, and the obvious repair is the one that removes the protection. I checked both steps and the guard rail holds — TestCompactionIsReadOnlyOverREST fails loudly if anyone tries it — so this costs a future contributor an hour, not a security hole. Worth noting too that event_test.go on main makes a stronger unqualified version of the same claim, so this is ours as much as yours. A clause naming Compaction as the exception would close it, in either file.

I've left two smaller notes on the lines themselves, about a subtest name and an unasserted fixture. Both are optional.

None of this blocks. If you'd rather not do another round after this wait, say so and I'll take the polish as a follow-up — please just rebase onto current main so it can go in.

Separately, and not for this PR: while checking what your tests pin I found several gaps that predate them. Nothing in the package marshals anything, so renaming a JSON tag on EventActions passes the entire suite while breaking every REST client. The nil-versus-empty map distinction that session.EventActions.MarshalJSON deliberately preserves is untested, as is whether the mappers alias or copy the caller's maps, and a new field mapped in only one direction would go unnoticed. I'll open an issue against the package for those — they are not yours to fix.