[primitives] Add sensitive-data redaction baseline

[justfinethanku]

What this does

• adds a new sensitive-data-redaction primitive with a canonical pattern catalog and adoption rules
• makes raw-text ingestion contributions declare and link that primitive in repo docs/templates
• applies the redaction pass to the Gmail and Obsidian importers before embeddings and storage
• records redaction metadata when replacements happen and skips truly high-risk payloads

Validation

• python3 -m py_compile recipes/obsidian-vault-import/import-obsidian.py
• deno check recipes/email-history-import/pull-gmail.ts
• JSON validation for new and updated metadata/pattern files

Merge note

If there are no objections, this will be merged by EOD.