Phase 15: Fix 17 tutorials with API signatures mismatched against actual codebase

[Copilot]

Re-audit of all 50 tutorials against src/ found 17 tutorials with code snippets that wouldn't compile — wrong parameter order, non-existent factory methods, renamed classes, incorrect return types. All fixed across 5 sequential chunks (075–079).

Milestones cleanup

Collapsed 490-line milestones.md to ~40 lines — removed all completed phase history and audit logs per the file's own enforcement rule ("contains only not-started chunks").

Tutorial fixes by chunk

• 075 (05, 06, 07) — PublishAsync params reversed (topic, envelope) → (envelope, topic); added missing string channel param to IPublishSubscribeChannel; replaced non-existent IntegrationPipelineResult.Succeeded()/.Failed() with record constructor
• 076 (13, 14, 29) — RoutingStep → RoutingSlipStep; _logging.RecordStage() → await _logging.LogAsync() (wrong name, wrong arity, missing await); AvailableTokens double → int; RemovePolicy void → bool
• 077 (31, 32, 37, 38) — IEventProjection.Apply() → ProjectAsync() (sync→async); OnboardAsync/OffboardAsync → ProvisionAsync/DeprovisionAsync with correct return type; src/Connector.FileSystem/ → src/Connector.File/; DiagnosticsConfig instance class → static class
• 078 (42, 44, 45, 46) — GetVariantAsync(flagName, tenantId) → (name, variantKey); WatchAsync IAsyncEnumerable → IObservable; replaced fictional DisasterRecoveryService with actual IFailoverManager/IDrDrillRunner; ProfilingSnapshot → ProfileSnapshot; HttpChannelAdapter : IChannelAdapter → HttpConnectorAdapter : IConnector
• 079 (49) — MapAck(envelope) → MapAck(Guid messageId, Guid correlationId)

Example fix (Tutorial 05):

// Before — parameters reversed, won't compile
await producer.PublishAsync("orders.created", envelope);

// After — matches IMessageBrokerProducer signature
await producer.PublishAsync(envelope, "orders.created");

Documentation-only changes — no source modifications, all 1,605 tests unaffected.