Add Scoverage code coverage reporting

[Copilot]

Integrates Mill's contrib-scoverage plugin for JVM code coverage analysis. Current baseline: 58.31% statement coverage, 52.71% branch coverage.

Configuration

• Build: Extended scautable.jvm with ScoverageModule trait (scoverage 2.3.0)
• Tests: scautable.test.jvm depends on scautable.jvm.scoverage for instrumented execution
• Reports: HTML, console, and XML (Cobertura) formats

Usage

./mill scautable.test.jvm.testLocal           # Run instrumented tests
./mill scautable.jvm.scoverage.htmlReport     # Generate reports
./mill scautable.jvm.scoverage.consoleReport

Coverage Analysis

Package	Coverage	Priority
io.github.quafadas.scautable.json	69.13%	-
io.github.quafadas.scautable	57.39%	Medium
io.github.quafadas (macro/type inference)	7.69%	High
CSV parsing core	43.40%	Medium

Recommendations

High priority:

• FirstN type inferrer: 0% coverage
• table object rendering: 11.54% coverage

Medium priority:

• CSV edge cases: delimiters, quotes, escaping, multiline fields
• Type inference combinations and null handling
• Excel integration paths

See COVERAGE.md for detailed analysis.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• mill-build.org
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Include scoverage reporting</issue_title>
<issue_description>https://mill-build.org/mill/contrib/scoverage.html

Include this module so that we know how much of this library is tested.

Make sure it runs and produces a sample output. Follow it up with a recommendation for where to improve coverage</issue_description>

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

• Fixes Include scoverage reporting #125

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.