[WIP] Convert single-module pom.xml to multi-module Maven reactor

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

---

This section details on the original issue you should resolve

<issue_title>[Java] Embed Rust CLI runtime 4.1: Parent POM restructure to multi-module reactor</issue_title>
<issue_description>## Overview

Convert the single-module java/pom.xml into a multi-module Maven reactor. Move the existing SDK code into a sdk/ subdirectory while preserving its GAV (com.github:copilot-sdk-java).

This is task 4.1 of 9 in the implementation plan. Tasks are assigned, completed, and merged serially in this listed order.

Branch: edburns/1917-java-embed-rust-cli-runtime-dd-3039145 on upstream

Plan and supporting resources

On the edburns/1917-java-embed-rust-cli-runtime-dd-3039145 branch, the directory 1917-java-embed-rust-cli-runtime-remove-before-merge contains the plan (1917-embed-cli-runtime-ignorance-reduction-plan.md) and supporting resources (spikes, prototypes, diagrams).

Read the entire plan before working.

Relevant plan sections to carefully re-read

• Section 3.1 — Maven module structure for per-platform classifier JARs — Resolution: Option B — hybrid multi-module reactor. The reactor structure is:

  java/
  ├── pom.xml                          (parent, packaging=pom, new GAV: com.github:copilot-sdk-java-parent)
  ├── sdk/
  │   └── pom.xml                      (existing SDK, KEEPS GAV: com.github:copilot-sdk-java)
  ├── copilot-native/
  │   └── pom.xml                      (new GAV: com.github:copilot-sdk-java-runtime)
  ├── copilot-native-all/
  │   └── pom.xml                      (optional monolithic: com.github:copilot-sdk-java-runtime-all)
  

  Key decisions: the existing copilot-sdk-java GAV is preserved (no breaking change); the parent POM is packaging=pom and internal-only; no dependency from copilot-sdk-java to copilot-sdk-java-runtime.
• Section 4.1 — Parent POM restructure (the primary task description)
• TDD discipline for all implementation steps — every step must follow test-driven workflow: write tests first, implement until green, refactor, gate before proceeding.

Deliverables

Files to create

1. java/pom.xml — New parent POM (com.github:copilot-sdk-java-parent, packaging=pom). Declares <modules> for sdk, copilot-native, and copilot-native-all. Centralizes shared properties, plugin versions, and copilot.sdk.root path. The copilot-native and copilot-native-all modules do NOT need to exist yet — they are created in later tasks. Include them in <modules> commented out or in a profile, so the reactor builds with just sdk for now.

Files to move

2. Existing java/pom.xml → java/sdk/pom.xml — Add <parent> pointing to copilot-sdk-java-parent. Preserve existing GAV com.github:copilot-sdk-java. All existing source, test, and resource paths must resolve correctly from the new java/sdk/ location.
3. Existing java/src/ → java/sdk/src/
4. Existing java/config/ → java/sdk/config/ (or keep at java/config/ and reference via ${project.parent.basedir}/config/ — choose whichever keeps paths simpler)

Files to update

5. justfile — Update java/ paths to java/sdk/ where needed.
6. .github/workflows/java-sdk-tests.yml — Update working directory references from java/ to java/sdk/ or java/ as appropriate for the reactor.
7. Any other workflows referencing java/pom.xml — search .github/workflows/ for references to java/pom.xml or java/ build commands and update them.

Gating tests and criteria

All of the following must pass before this task is considered complete:

1. Reactor build: mvn clean verify from java/ runs the full reactor successfully.
2. SDK-only build: mvn -pl sdk clean verify from java/ builds and tests the SDK exactly as before the restructure.
3. All existing tests pass: Every existing unit test and integration test passes without modification (unless path changes require adjustment).
4. CI workflows work: The updated workflow YAML files reference the correct directories and would run correctly.
5. GAV preservation: The SDK artifact's GAV remains com.github:copilot-sdk-java — no consumer-visible change.
6. Spotless compliance: mvn spotless:check passes.

Out of scope

• Creating the copilot-native or copilot-native-all module directories or POMs (tasks 4.7 and later).
• Any native binary handling, JNA dependencies, or FFI code.
• Changes to Java source code (only build/project structure changes).
  </issue_description>
• Closes ABORTED [Java] Embed Rust CLI runtime 4.1: Parent POM restructure to multi-module reactor #2143

Comments on the Issue (you are @copilot in this section)

• Fixes ABORTED [Java] Embed Rust CLI runtime 4.1: Parent POM restructure to multi-module reactor #2143

[Copilot]

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