phase 0: investigation and skeleton

- Read RFC-0001-v2.md end-to-end (canonical copy at java-sdk/RFC-0001-v2.md).
- PLAN.md: 4500-word engineering plan covering RFC walkthrough, message-type
  to record map, five state-machine diagrams (session, job, stream,
  subscription, lease), 16 documented open-question interpretations,
  integration test plan, and Java-specific design choices (sealed-interface
  envelope dispatch, virtual threads, structured concurrency, ScopedValue
  trace context, JSpecify + NullAway, JPMS).
- Multi-project Gradle skeleton (:lib, :cli, :examples) on Gradle 9.0.0
  wrapper with JDK 25 toolchain. Version catalog at gradle/libs.versions.toml.
- Spotless 7.0.4 with eclipse-jdt formatter (Palantir Java Format 2.68.0
  is currently incompatible with JDK 25 javac internals; documented in
  PLAN.md §A4 and the build files).
- Error Prone + NullAway wired up; gates green.
- Placeholder Version, ArcpCli, Example01MinimalSession source files so the
  three subprojects compile and the gate command set passes.
- README.md and CONFORMANCE.md (per-RFC-section status, all rows ⏳ pending).

Gate 0 verified: ./gradlew spotlessCheck check javadoc jacocoTestReport all
exit 0 with no compiler warnings on JDK 25.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nficano

.gitignore

@@ -0,0 +1,22 @@
+# Gradle
+.gradle/
+build/
+**/build/
+!gradle/wrapper/gradle-wrapper.jar
+
+# IDE
+.idea/
+*.iml
+.vscode/
+*.iws
+*.ipr
+.classpath
+.project
+.settings/
+
+# OS
+.DS_Store
+
+# JVM
+hs_err_pid*.log
+replay_pid*.log

CONFORMANCE.md

@@ -0,0 +1,70 @@
+# ARCP v1.0 Conformance Matrix — `arcp` (Java)
+
+This document tracks the implemented vs. deferred status of every section of
+[RFC-0001-v2.md](./RFC-0001-v2.md). It is updated at every phase gate.
+
+Legend: ✅ implemented · 🟡 partial · ⏳ deferred to v0.2 · ➖ not applicable
+
+| §    | Section                                    | Status |
+| ---- | ------------------------------------------ | ------ |
+| 1    | Goals                                      | ➖     |
+| 2    | Non-Goals                                  | ➖     |
+| 3    | Terminology                                | ➖     |
+| 4    | Design Principles                          | ⏳     |
+| 5    | Architecture                               | ⏳     |
+| 6.1  | Envelope                                   | ⏳     |
+| 6.2  | Message Types                              | ⏳     |
+| 6.3  | Command/Result/Event Flow                  | ⏳     |
+| 6.4  | Delivery Semantics                         | ⏳     |
+| 6.5  | Priority & QoS                             | ⏳     |
+| 7    | Capability Negotiation                     | ⏳     |
+| 8.1  | Session Establishment                      | ⏳     |
+| 8.2  | Credentials (`bearer`,`signed_jwt`,`none`) | ⏳     |
+| 8.2  | Credentials (`mtls`,`oauth2`)              | ⏳ v0.2 |
+| 8.3  | Runtime Identity                           | ⏳     |
+| 8.4  | Re-authentication                          | ⏳     |
+| 8.5  | Eviction                                   | ⏳     |
+| 9    | Sessions (stateless, stateful)             | ⏳     |
+| 9    | Sessions (durable across reconnect)        | ⏳ v0.2 |
+| 10.1 | Durable Jobs                               | ⏳     |
+| 10.2 | Job States                                 | ⏳     |
+| 10.3 | Heartbeats                                 | ⏳     |
+| 10.4 | Cancellation                               | ⏳     |
+| 10.5 | Interrupts                                 | ⏳     |
+| 10.6 | Scheduled Jobs                             | ⏳ v0.2 |
+| 11.1 | Stream Kinds                               | ⏳     |
+| 11.2 | Backpressure                               | ⏳     |
+| 11.3 | Binary Encoding (base64 in-envelope)       | ⏳     |
+| 11.3 | Binary Encoding (sidecar frames)           | ⏳ v0.2 |
+| 11.4 | Reasoning Streams                          | ⏳     |
+| 12.1 | Human Input Requests                       | ⏳     |
+| 12.2 | Choice Requests                            | ⏳     |
+| 12.3 | Provenance / multi-channel (first-wins)    | ⏳     |
+| 12.3 | Provenance / multi-channel (quorum)        | ⏳ v0.2 |
+| 12.4 | Expiration with default fallback           | ⏳     |
+| 13.1 | Subscribe                                  | ⏳     |
+| 13.2 | Filtering                                  | ⏳     |
+| 13.3 | Backfill                                   | ⏳     |
+| 13.4 | Termination                                | ⏳     |
+| 14   | Multi-Agent Coordination                   | ⏳ v0.2 |
+| 15.1 | Permission Model                           | ⏳     |
+| 15.2 | Sandboxing                                 | ➖ (runtime concern) |
+| 15.3 | Trust Levels                               | ⏳     |
+| 15.4 | Permission Challenge Flow                  | ⏳     |
+| 15.5 | Lease Lifecycle                            | ⏳     |
+| 15.6 | Trust Elevation                            | ⏳ v0.2 |
+| 16.1 | Artifact References                        | ⏳     |
+| 16.2 | Storage & Retrieval (inline base64)        | ⏳     |
+| 16.3 | Lifecycle / retention sweep                | ⏳     |
+| 17.1 | Tracing (SLF4J + ScopedValue)              | ⏳     |
+| 17.2 | Structured Logs                            | ⏳     |
+| 17.3 | Metrics + standard names                   | ⏳     |
+| 18.1 | Error Envelope                             | ⏳     |
+| 18.2 | Canonical Codes                            | ⏳     |
+| 18.3 | Retryability & Backoff                     | ⏳     |
+| 19   | Resumability (after_message_id)            | ⏳     |
+| 19   | Resumability (checkpoint)                  | ⏳ v0.2 |
+| 20   | MCP Compatibility                          | ➖ (advisory) |
+| 21   | Extensions                                 | ⏳     |
+| 22   | Reference Transports (WebSocket, stdio)    | ⏳     |
+| 22   | Reference Transports (HTTP/2, QUIC)        | ⏳ v0.2 |