chore: preserve local main changes for review

[forhappy]

Local main recovery snapshot

Preserves the reviewable uncommitted source and documentation found on local main before it is updated to origin/main.

Included

• Turso store-adapter and SQLite/Turso comparison sources and documentation.
• PostgreSQL benchmark sources, scripts, reports, and plans.
• Draft article, plans, and related documentation assets.
• The current working-tree version of the unresolved canonical-mutation design-file conflict.

Deliberately excluded

• Generated performance-results/ data, local databases/WAL files, Gradle cache, and external checkout directories.

Review notes

• This branch deliberately starts from the old local main commit so GitHub can surface integration conflicts against current main.
• Some Turso and benchmark code predates merged PR refactor: unify sync and async prolly engine #24 and is expected to be superseded by current main; it should be selectively salvaged, not merged wholesale.
• No validation was run because this is a preservation snapshot rather than an implementation change.