Snippets collection policy for lightweight practical notes

Decision

• Place lightweight practical notes (command fragments, minimal procedures, short config examples) in snippets.
• Operate with three content types: timeline posts in blog, knowledge/definitions in glossary, and practical fragments in snippets.
• Add the snippets collection and implement index/detail routes at /snippets and /{lang}/snippets.
• Keep _template.ja.md in the collection and exclude _-prefixed files from publication.

Context

The current content model had no clear home for short practical notes:

• Too thin for a blog post
• Not a definition page for glossary

Mixing these into blog blurs list intent and search intent.
At the same time, glossary is definition-oriented and does not fit command-centric snippets.

Options

• Option A: Keep short practical notes in blog.
• Option B: Put them under glossary.
• Option C: Add a dedicated snippets collection (chosen).

Rationale

• Readers get clearer entry points: posts, knowledge, and practical snippets.
• Isolating short notes helps preserve the quality bar of blog articles.
• URL separation improves clarity of page intent for search engines.

Consequences

• Add a snippets collection schema in src/content.config.ts.
• Add src/features/snippets/*, src/pages/snippets/*, and src/pages/[lang]/snippets*.
• Add snippets labels to header navigation and i18n dictionaries.
• Migrate the first content item (avifenc batch conversion memo) into content/snippets/.