feat(android): add registerEvent to the Kotlin SDK (#127)

[V3RON]

Closes #127

Stacked on #143 (issue #124); base is that branch.

What changed

The Kotlin core gets Appduct.registerEvent(name, description, payloadSchema) returning an EventRegistration. After every ack carrying event_registry: true, resume included, the client sends an event_registry_snapshot; later declarations and disposals send upsert and remove deltas. With no flag nothing is sent. The core-noop facade mirrors the API. Adds fixtures/event-registry-frames.json (snapshot, empty snapshot, upsert and remove deltas), which the Swift slice (#126) also adds in the same shape.

Acceptance criteria

#	Criterion	Test	Tier
1	Kotlin suite passes event-descriptors.json	FixturesConformanceTest event-descriptors fixture	unit
2	Every flagged ack, resume included, is followed by a snapshot	AppductEventRegistryTest snapshot, empty snapshot, resume ack tests	unit
3	The registration's disposer sends a remove delta	Appduct registerEvent ... its registration removes it	unit
4	No flag, no event frames	an ack without the flag sends no event frames, a resume ack without the flag ...	unit
5	Snapshot and delta frames fixture passes	the frames sent match every vector in event-registry-frames fixture	unit
6	Docs: Android README and install page; changelog	n/a	docs

E2E evidence

Target: Android emulator (Pixel API 35, Android 15, arm64), playground-native/android, commit 09ede49, this branch's daemon (isolated state dir, port 9611). The playground was temporarily patched, not committed, to call Appduct.registerEvent for cart.item_added (with a payload schema) and checkout.done (without).
Smoke: SMOKE_OK (throwing_tool returned tool_execution_error, exit 72)
Feature:

$ appduct events ls
  cart.item_added { sku: string, qty?: number }
    Posted when an item is added to the cart.
  checkout.done
    Posted when checkout completes.

$ appduct events ls --name cart.item_added
  Signature       cart.item_added { sku: string, qty?: number }
  Description     Posted when an item is added to the cart.
  Payload schema  {"type":"object","properties":{"sku":{"type":"string"},"qty":{"type":"number"}},"required":["sku"]}

$ appduct events ls --name checkout.done --json
{"ok":true,"data":{"events":[{"name":"checkout.done","description":"Posted when checkout completes."}],"total":1,"name":"checkout.done"}}

After backgrounding (HOME) and foregrounding the app, events ls and events ls --name cart.item_added --json returned the same declarations. The session stayed active throughout, so this shows persistence across background/foreground, not a new socket resume.

Checklist

• CHANGELOG.md has an entry under Unreleased
• User-facing docs updated (packages/native/android/README.md, website/.../install/android.mdx)
• No new import past a module's index.ts; no new direct node:* I/O outside an adapter
• Simplification checklist applied
• docs/ARCHITECTURE.md unaffected

Out of scope

fixtures/README.md still says the event descriptors fixture is asserted by TypeScript only and does not describe event-registry-frames.json; it is #124's file, so left for the stack to reconcile with #126.

Status

Implement: done (5/5 green) Review: round 2, approve E2E: pass (Android, playground-native) Ready: yes

[V3RON]

Request changes (posted as a comment: GitHub refuses request-changes on your own PR): 1 blocker, 0 should-fix.
Spec: issue #127 plus the ordering contract in packages/native/fixtures/README.md.
Fix first: an event declared from a connection listener during the ack goes out as a delta before the snapshot that then wipes it.

[V3RON]

Blocker: a declaration made while the ack is handled is sent as a delta before the snapshot, and the snapshot then erases it on the daemon.

setClientState(active) and emitSessionChange run listeners synchronously on the dispatcher before this line. A listener that declares an event, e.g. Appduct.addListener { if (it is AppductEvent.SessionChange) Appduct.registerEvent("x", "d") }, enqueues the upsert coroutine ahead of the sendSnapshotSafely launch below, and this snapshot is taken before that coroutine has upserted. The dispatcher then runs the upsert first: state is active and the session accepts, so the delta is sent; the snapshot follows without x. The daemon's registry.snapshot replaces the whole map, so x is gone from appduct events ls until the next resume. A registerEvent call from another thread that lands between the continuation starting and the launch below hits the same order.

Reproduced on this head with a scratch test: client.addSessionChangeListener { _, _, _, _ -> client.registerEvent(event("from_listener")) } then connectAndAck(eventRegistry = true) sends [event_registry_delta:from_listener, event_registry_snapshot:[]]. This breaks the fixtures README contract (snapshot before any later delta).

Fix direction: gate deltas on a per-ack "snapshot sent" flag that the snapshot task sets, and read the event registry inside that task (under sendLock) instead of here.

[V3RON]

Approve (posted as a comment: GitHub blocks approving your own PR): 0 blocker, 0 should-fix. Spec: issue #127 via the PR's criteria table.
Round 1's ordering blocker is fixed: a declaration or removal made while an ack is handled lands in that ack's snapshot and sends no delta; the event registry suite passed 25 of 25 reruns and the two new tests fail on 6dca660 without the fix.