fix: audit Korean Markdown emphasis across all posts

[CoBool]

Problem and changes

A parser and final-HTML audit of all 12 content/posts files found 7 remaining emphasis failures across 3 posts: double quotes (2 occurrences), single quotes, a closing parenthesis, percent signs (2 occurrences), and inline-code backticks before Korean particles. Move punctuation outside strong delimiters, or include the particle when preserving inline code. Also escape currency dollar signs in 2 Astra paragraphs that remark-math otherwise consumes as math.

Post changes are exactly 9 lines across 3 files. Compared every post against main: all line counts and all text are preserved after removing only emphasis markers and currency escapes. PR #120 is already merged; its quoted Astra sentence remains covered.

Regression coverage

• Audit every authored post, including drafts, through the actual Markdown processor AST and final HTML; code examples are excluded from prose checks.
• Assert exact strong content and occurrence counts in actual posts, including both repeated quotations and currency.
• Add punctuation-boundary unit cases.
• Playwright checks built pages for visible strong elements, computed font weight, literal-star absence, absence of unintended math, and paragraph screenshots.

Validation

• Lint and typecheck passed.
• 42 test files / 303 tests passed.
• Production build, Pagefind and export validation passed.
• All 7 Playwright tests passed (3 post regressions plus 4 existing browser smoke tests).
• Local Windows port 4173 was unavailable; a temporary configuration outside the repository used 4174 for the same tests. CI configuration remains unchanged.
• Reviewed all captured paragraph images and the complete diff. No parser behavior changes or dependency changes.