feat(audience): mirror server-side event validation client-side [SDK-679]

[nattb8]

Summary

Ticket: SDK-679

Brings client-side validation in the Audience package to parity with the ingest API. Invalid calls (empty/malformed id, identical alias ids, a null/empty typed event) now throw immediately instead of dropping silently with a Log.Warn that's easy to miss; valid calls are unaffected and still enqueue as before. The passport-ID format check already covered part of this scope (bac4b2fc); this closes the rest.

Gap	Before	After
Alias() equality check	Not checked at all	Throws on fromId == toId, matching the backend (ignores identityType)
Identify()/Alias()/Track() caller-bug input (empty id, malformed passport id, identical alias ids, empty event name, null IEvent)	Logged via Log.Warn and silently dropped	Throws (ArgumentException/ArgumentNullException)
Track() validation order	Checked the argument after the consent gate, so Track(null)/Track("") at None consent silently no-opped instead of throwing, unlike Identify()/Alias()	Argument validated before the consent gate, matching Identify()/Alias()
Clock-skew future bound	Not checked (only the past bound existed, coincidentally)	Files stamped more than 24h in the future are also excluded now
Sample app (AudienceSample.cs) mirror accuracy	Only checked for empty ids	Also checks equality, kept in sync with the fix above
Sample app flush outcome visibility	Only an app-tier "flush() Ok" row confirming the async call didn't throw — no signal for whether the actual send succeeded	SDK now logs a per-attempt "flush ok/failed (N messages)" outcome (mirrors the TS SDK's logFlush); sample app gives it its own Ok/Err row with the message itself as the label, matching the web sample app's console-mirror instead of the generic "sdk" tag used for other SDK-sourced messages

Consent-gated no-ops (e.g. Identify() below Full consent) and a buggy consumer IEvent.ToProperties()/EventName implementation still just log a warning: the first is routine flow-gating, not a caller bug; the second is third-party code we can't trust not to crash the game.

Sample app (AudienceSample.cs): OnAlias()/OnIdentify() already run through RunAndLog, which catches and displays thrown exceptions, so no new plumbing was needed. The OnAlias() mirror check now tracks only the one case it can still detect, consent below Full, since the id/equality checks it used to make now throw before reaching it. Added a live-fire UI test (Alias_SameId_Throws), matching the existing passport-ID test's pattern.

Test plan

• dotnet build src/Audience.Build/Audience.Tests/Audience.Tests.csproj — no errors, only pre-existing unrelated warnings
• dotnet test — 382 passed, 1 skipped (pre-existing), 0 failed; includes coverage converted from Log.Warn assertions to Assert.Throws, new tests for the flush-outcome log on both success and failure, and regression tests proving Track() throws even at None consent
• dotnet format --verify-no-changes on all changed files — clean
• Unity Editor Test Runner not run here (can't execute in this environment) — needs a pass before merge, especially Alias_SameId_Throws, Identify_PassportWithInvalidIdFormat_Throws, and the AudienceSample.cs sample app fix (including the new flush-outcome log row)

🤖 Generated with Claude Code

[github-actions]

Audience SDK — Build Size

Platform	SDK Size	Change
Android	0.37 / 20.00 MB	+0.01 MB	✅
Windows	0.17 / 20.00 MB	+0.01 MB	✅
iOS	8.55 / 20.00 MB	+0.03 MB	✅
macOS	0.92 / 20.00 MB	+0.02 MB	✅

SDK Size = build minus empty app. Change = vs baseline. Fails if any platform exceeds its absolute size limit.