Closes #15: Docs: add source-backed Korean mixed-script UI examples - #21

Thanks — the mixed-script section is a useful direction for #15, but this head is not merge-ready. Required changes: (1) run node extensions/learning/runtime/scripts/build-learning-catalog.mjs and commit extensions/learning/runtime/catalog.json plus extensions/learning/runtime/references/learning-catalog.json. Exact head 0e1e449 leaves both files modified after the CI generator sequence, so git diff --exit-code will fail. (2) The Do value 12,400원 and the Do-not value 십이만사천원 are not equivalent: the latter is 124,000원. Compare the same value, for example 일만 이천사백 원. (3) The cited Toss URL /design/ux-writing.html no longer identifies that document; its Markdown form returns Page Not Found and the HTML path resolves to the generic design page. Replace it with a current direct primary source such as https://developers-apps-in-toss.toss.im/design/consumer-ux-guide.md, and either source the tabular-numerals requirement separately or narrow that claim. The National Institute source supports attaching unit nouns to Arabic numerals, not tabular numeral rendering. (4) Link parent issue #8 as required by #15. (5) Correct the PR statement that the repo ships no test suite and report the actual validation commands/results. Please ping after updating and I will re-run the exact-head checks.

Maintainer review: this head is not merge-ready. (1) Run node extensions/learning/runtime/scripts/build-learning-catalog.mjs and commit extensions/learning/runtime/catalog.json plus extensions/learning/runtime/references/learning-catalog.json; exact head 0e1e449 leaves both dirty and will fail git diff --exit-code. (2) 12,400원 and 십이만사천원 are different values; compare the same amount, for example 일만 이천사백 원. (3) The cited Toss /design/ux-writing.html page is no longer a direct source. Replace it with a current primary source such as https://developers-apps-in-toss.toss.im/design/consumer-ux-guide.md, and separately source or narrow the tabular-numerals claim. (4) Link parent issue #8. (5) Correct the no-test-suite statement and report actual validation results. Please ping after updating for exact-head re-review.

Maintainer review on exact head 0e1e449: (1) regenerate and commit extensions/learning/runtime/catalog.json and extensions/learning/runtime/references/learning-catalog.json; both are dirty after the CI generator sequence. (2) 12,400원 and 십이만사천원 are different values; compare an identical amount. (3) Replace the removed Toss /design/ux-writing.html source with a current direct primary source and separately source or narrow the tabular-numerals claim. (4) Link parent issue #8. (5) Correct the no-test-suite statement and report actual validations. Please ping after updating for exact-head re-review.

Thanks for adding source-backed Korean mixed-script examples. I tested a synthetic merge against current main (8a1ce9b). Public-claim checks, all 63 runtime tests, engine validation, Markdown links, and the 134-page Next.js production build pass.

Two changes are required before CI approval:

1. The money example compares 12,400원 with 십이만사천원, which is a different amount. Please make the Do and Do-not examples semantically identical so the example tests writing style rather than changing the value.
2. The final generated-file drift gate fails because extensions/learning/runtime/catalog.json and extensions/learning/runtime/references/learning-catalog.json were not regenerated after the engine revision changed.

Please rebase onto current main, regenerate the context, learning, and llms catalogs, commit every generated output until git diff --exit-code is clean, and update the PR description because the repository now has a runtime test suite and CI gates.