docs: bring CLAUDE.md up to date with the psycopg and turso drivers

[rayakame]

CLAUDE.md still described three drivers; the list grew to seven in v0.7.0/v0.8.0.

• Driver list: asyncpg, psycopg_async, psycopg_sync (postgres); aiosqlite, sqlite3, turso_async, turso_sync (sqlite). Per-family command support noted (:copyfrom postgres-only, :execlastid sqlite/turso-only, :batch* never).
• Commands: nox sessions generalized to one per driver; verification loop now says all seven *_check sessions; build section notes the hardcoded driver dir lists (build scripts, noxfile DRIVER_PATHS, ci.yml) to touch when adding a driver.
• Architecture: converters and speedups options; psycopg_sql.go placeholder rewriter; reserved-locals seeding in plainParams; all four driver implementation files and how conversion differs per family.
• Invariants: psycopg loader registration is process-global like sqlite converters; speedups swaps decodes to ciso8601; converter functions are never called with None and convert lists element-wise.

Doc-only change, no generated output affected; labeled skip-fragment-check.

[codecov]

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