Reference the standalone sample as a pinned git submodule; its CLAUDE.md rules do not apply here

[RyazanovAlexander]

What

• Replace the hand-refreshed, gitignored snapshot under reference/mathtrail-standalone/ with a git submodule of MathTrail/mathtrail-standalone, pinned to c6cbeb2 (v0.6.8); .gitmodules names main for --remote.
• The sample's CLAUDE.md now keeps its name, so:
  • .claude/settings.json sets claudeMdExcludes to the sample's own path, so Claude Code does not load its CLAUDE.md/CLAUDE.local.md;
  • CLAUDE.md states that any CLAUDE.md under reference/ is another repository's rules and binds nothing here.
• Keep the sample out of everything that is about this repository:
  • .gitignore still ignores everything else under reference/;
  • .ignore keeps ripgrep-based search out of it;
  • sonar.exclusions keeps the analysis out of it;
  • .dockerignore keeps .gitmodules and .ignore out of the build context;
  • git.detectSubmodules: false keeps it out of Source Control.
• post-start checks the submodule out after a fresh clone (120 s cap, no credential prompt) and sets submodule.recurse, so a pull that moves the pin moves the sample.
• Docs: the CLAUDE.md Reference copies section is rewritten (rsync and the host-side refresh are gone); decision R70 is added and R46 amended; RUN.md and stack.html are updated.

CI is unaffected: actions/checkout fetches no submodules.

Checked

• ci-lint, ci-test, ci-mocks-check, ci-licenses, ci-vuln, ci-secrets, ci-workflows, tf-check, release-version, ci-image-smoke, ci-image-scan, release-artifacts are green.
• post-start checks the submodule out again after git submodule deinit.
• The exclusion globs match the sample's files at any depth and never this repository's own CLAUDE.md.

[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