docs(harness): enforce bilingual docs

[egdev6]

Summary

Fix the paired docs language split and add a harness guard so base *.md docs stay Spanish while matching .en.md docs stay English.

Closes #261

Review scope

• Primary files/areas:
  • docs/COMPONENTS.md restored as the Spanish counterpart to docs/COMPONENTS.en.md.
  • .atl/AGENTS.md, .atl/skills/pr-reviewer/SKILL.md, and docs/CONTRIBUTING*.md now document/review the bilingual docs rule.
• Out of scope:
  • Component runtime behavior.
  • Storybook story rules and linked-issue gates already merged in docs(harness): document workflow gates #262.
  • Existing local/unrelated .gitignore, .atl/skill-registry.md, reviews/, and sdd-init-result.md changes.
• Review workload: medium; mostly a Spanish docs restoration for a long reference file.

Type of change

• New component
• Existing component update/refactor
• Bug fix
• Accessibility
• Design tokens
• Storybook/docs
• Infrastructure/tooling
• NPM/dependencies

Workflow gates

• Linked issue is present with Closes #NNN or maintainer approved an exception.
• Linked issue has label status:approved before implementation starts.
• Linked issue assignee was checked before work started; issue is assigned to @egdev6.
• Work was started through the Project flow: assignee set, Project status In progress, branch/worktree recorded.
• PR title follows Conventional Commit format: <type>(<optional scope>): <description>.
• Commits follow the same commitlint-enforced format.
• Diff is focused; unrelated work is called out in Review scope.
• MCP/runtime artifacts are absent: .playwright-mcp, page-*.png, page-*.jpeg, *.md.playwright-output.

Component evidence (required for component changes)

N/A — docs/harness-only change.

Accessibility evidence

N/A — docs/harness-only change.

Validation evidence

• TypeScript: lefthook pre-commit ran typecheck — passed.
• Unit tests: lefthook pre-push ran pnpm test — 33 files / 629 tests passed.
• Build/package: not run locally; docs/harness-only change.
• Storybook or visual check: not run locally; no component visuals changed.
• Accessibility check: not run locally; no runtime accessibility changed.
• Security/dependency check: not run locally; no dependency changes.
• Diff hygiene: git diff --check passed.
• Bilingual docs check: docs/COMPONENTS.md is Spanish; fenced code blocks match docs/COMPONENTS.en.md exactly (95/95).
• Review: fresh reviewer reported no blockers for the Spanish docs fix and bilingual harness rule.

Screenshots or recordings

N/A — docs/harness-only change.

Notes for reviewer

This is a follow-up to #262. It fixes the Spanish/English paired docs mistake and adds a harness so future PRs reject the same failure mode: base *.md must stay Spanish, matching .en.md stays English, while Storybook/code/comments/identifiers remain English.