docs: migrations blog post and README pointer - #110

What

• content/blog/migrations-as-data.mdx: 'Migrations as Data: Schema Versioning Where Rules Are Schema Too'. The three design decisions worth telling: (1) rules and indexes are versioned schema alongside relations, and revert restores the previous logic with incremental retraction; (2) the applied-migrations ledger is facts in the KG, queryable like everything else; (3) migration files are language-neutral JSON - typed operations deriving both forward and reverse IQL, provably consumable without Python (the jq demo). Includes the command surface and the honest edges (no ALTER means drop+recreate loses data; per-operation sequencing, failures loud and never recorded as applied).
• README: one pointer to il migration from the CLI section.
• front/lib/content-bundle.ts regenerated (12 posts).

Merge order

After #109 + #101, which ship the commands and format the article describes. No file conflicts with any open PR.