PR1: Standardize emulator reset() contract + conformance test

[dksingh1997]

Tier 1 — PR 1 of 4 (control plane foundation)

First PR toward the control plane (see PLAN.md). Establishes the emulator contract every service must follow so the launcher, probe, and forthcoming control-plane server can introspect and reset any emulator uniformly.

What changed

• Standardized reset() across the catalog. Audited all 250 services; 6 networked emulators lacked a reset() method — added it to cassandra, kafka, mysql, rabbitmq, elasticsearch, and supabase. State initialization moved into reset() and called from the constructor, so state init and reset can never drift. Behavior-preserving — only refactors where state is initialized.
• New conformance meta-test (test/conformance.test.ts). Across the whole catalog it asserts:
  • every manifest is valid (name, port, protocol) and the name matches the slug,
  • ports are unique catalog-wide,
  • every networked service ships src/server.js exporting a *Server class,
  • that class implements start(), stop(), and reset(),
  • plus a live boot → /health → reset() smoke test for a representative sample (stripe, openai, s3, sendgrid, elasticsearch, supabase, pinecone, github).
• Docs: CONTRIBUTING.md now documents the full contract (reset() required; all state initialized in reset()) and the PR checklist references the conformance test. Added CHANGELOG.md. Added PLAN.md (10-PR roadmap) and SKILL.md (implementation guide for agents).

Why

A reliable reset() is the prerequisite for per-test isolation and for the control plane (PR 2) to wipe state between test cases without restarting containers. The conformance test prevents convention drift as the catalog grows (the apigateway-stub class of problem).

Verification

• Full suite green on 3 consecutive runs: 252 files / 5466 tests (was 5457; +9 from conformance).
• Edited services' own real-driver test suites pass (79 tests across the 6).
• Live real-driver round-trips confirmed for the 4 edited TCP services: mysql SELECT 1, kafka listTopics, rabbitmq assertQueue, cassandra system.local.

Contract (now documented)

export class MyServiceServer {
  constructor(port, options) { /* config only */ this.reset(); }
  reset() { /* clears ALL in-memory state; idempotent, no I/O */ }
  start() { /* resolves once listening */ }
  stop()  { /* resolves once closed */ }
}

Part of: Tier 1 control plane. Next: PR 2 (control-plane HTTP server).