chore(release): bump version to 0.12.3-SNAPSHOT, rules baseline to 0.12.2

[rabestro]

Post-release bookkeeping for v0.12.1 and v0.12.2, opened manually after Ops: Release
failed on both cuts at the "Publish both packages to npmjs.org through the canonical workflow"
step (registry-integrity-propagation timeout in .mise/lib/npm-publish-if-missing.sh), which
also skipped the automatic "Create GitHub Release" and "Open the next-SNAPSHOT version-bump
pull request" steps for both releases.

What was already recovered manually, outside this PR:

• @fortemate/dicechess-engine@0.12.1 / -wasm@0.12.1 and @0.12.2 / -wasm@0.12.2 are
  published on npmjs.org (verified via npm view).
• GitHub Releases v0.12.1
  and v0.12.2 were created
  with the exact assets from each run's immutable npm release bundle artifact.

This PR does the one remaining piece: sets build.sbt version to 0.12.3-SNAPSHOT so main
carries the next development version, and moves RulesMimaBaseline to 0.12.2 (the latest
actual release) so the rules binary-compatibility gate compares against it. Nothing else changes.

Note: PR #266 already raised NPM_VERIFY_MAX_ATTEMPTS/NPM_VERIFY_SLEEP_SECONDS (30s → 120s)
in response to the v0.12.1 failure, but the v0.12.2 run still hit the same timeout — npm registry
propagation exceeded even the increased budget. Worth a follow-up (e.g. treat the propagation
check as non-fatal, since npm publish itself already succeeded by that point).

🤖 Generated with Claude Code

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Repository: fortemate/dicechess-engine/.coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 67033458-aec5-4cd7-b5c9-ca0f21628323

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[hacktron-app]

Hacktron Security Check - Skipped

Reason: OSS PR review limit reached for this approved repository and developer. New OSS PRs for this repository will resume at the start of the next cycle.

Wait for the next cycle. OSS quota is limited to the approved OSS repository and cannot be used on paid repositories.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud