feat!: 2.0 — both-engines config, sqlSwitch rename, db.reconnect()

[revxshafi]

Summary

Breaking 2.0 release. Reshapes the config to declare both engines up front, renames the factory, and adds a db.reconnect() primitive.

• Config reshape (breaking):DALConfig.db is now a 'local' | 'cloud' selector with local? / cloud? blocks declared alongside it. The per-block mode field is removed. Every declared block is validated eagerly at connect(), so a bad cloud connectionString is caught at boot even while running db: 'local'; db: 'cloud' with no cloud block throws ConfigurationError.
• createDAL() → sqlSwitch():sqlSwitch is the factory and default export. createDAL stays as a one-line @deprecated alias (removed in 3.0).
• db.reconnect(target?): one primitive for three jobs — restart a wedged connection, recover a lost one, or repoint to the other declared engine without moving data. Fail-safe: the replacement engine is built and validated before the old one is torn down, and pending writes are flushed first. engineSwap() stays a pure data-mover.
• Docs + version: README, CHANGELOG.md (2.0.0 entry + migration notes), CLAUDE.md public-API invariant; bumped to 2.0.0 across root + scoped package (version + dep pin).
• SVG fixes:architecture.svg engineSwap caption shrunk to 13px so "resumable" stops overflowing; "collapses repeats" → "collapse repeats". hero.svg drops the hand-edited npm 1.0.1 chip for the always-true ESM + CJS, and mode: → db: to match the 2.0 shape.

Related issue

none

Type of change

• Breaking change (fix or feature that changes existing behavior or the public API)
• Documentation only (SVG + README + CHANGELOG)

How it was tested

pnpm check # Biome lint + format — clean
pnpm typecheck # tsc --noEmit on src/ + scripts — 0 errors
pnpm build # tsup dual CJS/ESM — ok
pnpm docs # TypeDoc zero warnings — ok

Logic + fakedriver tests pass locally (including the new test/reconnect.test.ts and test/factory-rename.test.ts). The real-SQLite/Postgres integration matrix could not run in the Replit sandbox (native better-sqlite3 ABI mismatch segfaults the Vitest fork) — that matrix runs authoritatively in CI on Node 22/24 once this lands on main.

Checklist

• Tests added or updated for the change
• Docs / TSDoc updated where relevant
• TypeDoc still builds at zero warnings (pnpm docs)
• Public API surface (src/database/index.ts) changes are intentional and called out above
• Follows the conventions in CLAUDE.md

Supersedes #19 (rebased onto current main to drop a duplicate README commit that was showing as a conflict).