exploration: add typed client event API

[wouter173]

Summary

• add a typed makeEvent API for joined-room sync events
• decode and refine custom event content before invoking handlers
• route MatrixClient.onEvent through event definitions instead of raw sync-frame predicates
• update the client example and add runtime/type-inference coverage

Verification

• full workspace TypeScript typecheck
• formatting check
• 74 package tests
• diff whitespace check

Closes #8

[wouter173]

Review summary: the typed makeEvent API, schema-failure filtering, public export, inference coverage, and example are well structured. One correctness issue remains in joined-room extraction: state events duplicated between state_after and timeline are delivered twice. Please deduplicate merged events by eventId and add a regression test. Focused makeEvent tests pass (3/3).

[wouter173]

[P1] Deduplicate state_after against timeline events. With use_state_after=true, state_after covers updates through the end of the timeline, so a state event can also be present in timeline. Concatenating both arrays invokes the subscription callback twice for the same event. Please deduplicate the merged events by eventId (while retaining timeline-only/intermediate events) and add a regression test with the same state event in both arrays.

[wouter173]

Fixed in 4bf911b. joinedRoomEvents now deduplicates per room by first occurrence of eventId across the selected state source followed by the timeline. This preserves the existing state-before-timeline order, gives the state copy precedence when an event appears in both, and retains timeline-only/intermediate events. The regression uses a conflicting duplicate payload to verify precedence; focused tests pass 4/4 and the full package suite passes 75/75.