Milestone 1 — v1.0 wire alignment (10 sub-PRs)

[nficano]

Goal

v1.0 wire alignment — the foundation. The largest milestone, split into 10 sub-PRs so reviewers can land them incrementally.

Sub-PRs

• 1A: New Envelope (8 fields per §5.1) + manual Codable for type discriminator
• 1B: Message enum + v1.0 message types: session.hello/welcome/bye/error, job.submit/accepted/event/result/error/cancel
• 1C: 2-step session handshake (hello/welcome) + ResumeToken rotation in ARCPRuntime
• 1D: event_seq session-scoped monotonic counter; replay keyed on last_event_seq
• 1E: Unified job.event envelope; JobEventBody enum for 8 v1.0 kinds
• 1F: Lease model rewrite: immutable Lease value type, Capability enum with xVendor(String), Pattern glob compiler, LeaseEvaluator.authorize
• 1G: Error code overhaul: 12-case v1.0 ARCPError. Drop gRPC-style codes
• 1H: Delegation (event-kind, not envelope-type): delegate body, parent-trace inheritance, LEASE_SUBSET_VIOLATION on subset failure
• 1I: Strip dead surfaces: HITL, Artifacts.swift, Streaming.swift, etc. Move JWT auth to opt-in ARCPAuthJWT target. Drop SQLite from default
• 1J: Target split per 04-architecture.md §1: rewrite Package.swift, move files into Sources/ARCP{Core,Client,Runtime}/. Add ARCPWebSocketClient shell

Definition of done

A submit-and-stream example compiles and round-trips through MemoryTransport against v1.0 spec-shaped envelopes, with no v1.1 features.

Spec §

§5.1, §6, §7.1–§7.4, §8.1, §8.2, §9.1–§9.4, §10, §12, §14