fix(preview): break Korean between words on the showcase pages (D-030)

[jlc488]

Summary

The showcase split Korean mid-word, because browsers break Hangul between any two syllables by default. For example "브랜드 면 위 텍 / 스트는" and "미달합 / 니다". Measured as served at devslab.kr/dds/ (Edge, per-character line boxes, breaks between two Hangul syllables):

page	375px	1440px
index.html	22	5
components.html	3	1
icons.html	3	0

Each preview page now puts two rules on its language root, which children inherit:

:where([lang|="ko"]) { word-break: keep-all; overflow-wrap: break-word; }
:where([lang]:not([lang|="ko"])) { word-break: normal; overflow-wrap: normal; }

• Korean only. Japanese and Chinese have no spaces between words, so keep-all there would remove their only break points. Elements that declare another language go back to the default.
• break-word, not anywhere. anywhere also shrinks Latin min-content to one letter; devslab.kr saw "cya / n" in a narrow flex cell.
• :where(), zero specificity. Any page or component rule wins.

Not in dds.css (D-030)

A base.css default would change Korean line breaking in every product that loads dds.css (VisionLinq, AskLinq, BookLinq, TraceLinq, FM덴탈) on its next bump. keep-all widens the min-content of Korean table cells and chips, so each product would need a 375px check. D-029 left Korean kicker tracking to each product's root for the same reason. It also would not have fixed index.html, which does not load dds.css. Spec 3.2 (en + ko) now tells product pages which two rules to put on their root. D-030's revisit condition: when a second family product after devslab.kr adds the same rule.

Verification

• tests/foundation-contracts.test.mjs: new contract pinning the rule on all three pages, no per-element word-break, and no keep-all in dds-css/src. It failed before the change ("preview/index.html must set keep-all on its Korean root"); 11/11 pass after.
• Locally green: verify:source:stage1-2 (22), verify:source:stage3-4 (43), verify:foundation:core, and the full pnpm run verify (docs sync; devslab/asklinq consumer copies in sync). Only check-docs-sync.mjs and the contract test read preview/*.html or the docs, so I didn't run the browser, Storybook or canary jobs locally. CI runs them.
• Measured after the change, all three pages at 320, 360, 375, 390, 414, 768, 1024 and 1440px: 0 breaks between syllables, no new horizontal overflow, no text escaping its box. icons.html overflows at 320px (the top nav link reaches 336px), exactly as before this change.
• Screenshots checked at 375/1440 before and after: line counts and component sizes are unchanged. Only the break positions moved.

Known limitation, disclosed rather than fixed: Chromium's keep-all glues only letters and digits, so a particle can still start a line after a closing quote, an ellipsis or ).

The consumer resync at devslab.kr is jlc488/devlab.kr#76 (it vendors this branch; merge this first).