Add french and korean seed content

What does this MR do?

Enables French (fr-fr) and Korean (ko-kr) as additional target locales for GitLab Runner documentation, mirroring the existing Japanese (ja-jp) setup.

This is the runner-side counterpart to gitlab-org/gitlab!234689, scoped to what this repo actually needs (see "Differences from gitlab-org/gitlab" below).

Changes

• .gitlab/CODEOWNERS — adds /docs-locale/fr-fr and /docs-locale/ko-kr ownership rules for the French and Korean localization maintainer groups (alongside tech-docs). Also reorders the existing ja-jp line to put tech-docs first for consistency.
• docs-locale/fr-fr/_index.md and docs-locale/ko-kr/_index.md — seed files so the locale directories exist and CODEOWNERS rules have content to match.
• scripts/lint-i18n-docs — broadens the lychee --exclude pattern from ja-jp/development.*# to (ja-jp|ko-kr|fr-fr)/development.*# for parity. Low impact in practice because argo_translation.yml already ignores docs/development/** for every target language.
• .gitlab/.argo/mr_template_doc_ai.md — the auto-generated translation MR template now lists Japanese, French, and Korean maintainer groups for Duo-flagged review handoffs. Also fixes pre-existing typos on line 4 (/doc → /docs, /doc-locale → /docs-locale).

argo_translation.yml already lists [fr-fr, ja-jp, ko-kr] as target languages, so no change there.

Reviewer Notes - Differences from gitlab!234689 (merged)

I noticed some differences to the runner project compared to GitLab. The GitLab MR adds quite a bit of per-language scaffolding to the GitLab repo (per-locale .vale.ini files, per-locale rule directories, per-language CI patterns like .docs-ko-kr-patterns, per-language Vale lint jobs, route-map entries, Danger specs). Most of that doesn't seem to apply to gitlab-runner. The runner repo's i18n linting and verification are already language-agnostic. Enabling a new locale here mainly means landing the directory, the CODEOWNERS rule, and updating the few places that still hardcode ja-jp.

Concern	gitlab-org/gitlab	gitlab-runner
Vale config	Per-locale .vale.ini + locale rules dir	Single shared root .vale.ini with --filter='.Name matches "gitlab_docs"' applied to all locales
CI rule patterns	Per-language (.docs-ja-jp-patterns, etc.)	Single generic .docs-i18n-patterns covering docs-locale/**/*
Lint jobs	Per-language (docs-i18n-lint korean-vale, etc.)	Single docs:lint i18n markdown job covers all locales
Route map	Per-language entries	Generic regex covering all docs
Path verification	(not present)	Generic scripts/docs-i18n-verify-paths matching ^docs-locale/[^/]+/(.+)$

Why was this MR needed?

Enabling third party vendor to start translating and delivering contents in french and korean.

What's the best way to test this MR?

• Pipeline runs green on this branch
• Pull branch down
• docs:lint i18n markdown job runs and processes both new locale dirs
• docs:lint i18n paths job confirms English originals exist for both seeded files
• CODEOWNERS rules trigger the expected maintainer groups on this MR

What are the relevant issue numbers?

Closes gitlab-com/localization/docs-site-localization#880 (closed)