docs: add Sourcey reference for Testcontainers

[fengyangxxx]

Summary

• Add 25 Sourcey-generated Testcontainers for Java reference pages under docs/sourcey/.
• Preserve generated navigation, examples, configuration guidance, module pages, source links, and LLM/search indexes.
• Keep the target-owned publication route at /sourcey/ through the existing MkDocs/Netlify documentation build.

Exact package

• Source pin: testcontainers/testcontainers-java@deb78e1e6e47675f56e8d7b3f4747093d66f1baa
• PR base: testcontainers/testcontainers-java@2ac3c9773ca52381266463c3709c37155e190b68
• Proposed head: fengyangxxx/testcontainers-java@1b97470cdfcce456124c0fd71dbb762db6d156e7
• Changed paths: 58 additions under docs/sourcey/, 1,530,020 bytes
• Package tree SHA-256: 3330682bde81c85f8904a2f8b2964dfe0552936ff4aa049ad6c8a3067c255760
• Sourcey: 3.6.3, MkDocs adapter
• Generation command: node node_modules/sourcey/dist/cli.js build --output dist
• Config: sourcey.config.ts with selected navigation in sourcey-target.mkdocs.yml

Validation and maintenance

• All 25 selected navigation pages have source-to-generated byte mappings.
• The official pinned MkDocs dependency build compared all 58 package files byte-for-byte with zero mismatches.
• The replay on current main adds only the package paths and passes git diff --check.
• Regeneration requires rerunning Sourcey against the pinned or deliberately updated upstream source and reviewing the generated diff. Committing static output makes /sourcey/ deployable by the existing site, but maintainers would own review of generated updates and repository size.

Provenance boundary

This is claimant-authored work prepared after the Frantic #46 claim. Discussion #11930 has no maintainer response and refers to an older pre-cleanup package; it is not approval, adoption, endorsement, merge, or deployment of these bytes. Opening this PR is an adoption request, not approval, adoption, endorsement, merge, or deployment. Merge and target-owned Netlify deployment remain entirely at maintainer discretion.