Align CLI documentation with its PostgreSQL runtime dependency

Context

Raised while reviewing #43. README.md calls the operator CLI “zero-dependency”, but the published package declares postgres. facility instance bootstrap imports and opens that client, and the authentication guide explicitly documents its direct PostgreSQL connection.

Problem

The package-level “zero-dependency” claim no longer matches the deliberate PostgreSQL-backed instance bootstrap added in e92c706. It misstates the published artifact's runtime contract and can send future reviews toward removing behavior the self-host bootstrap requires.

Proposed change

Replace the blanket claim with wording that accurately describes the CLI, and audit the public CLI/package documentation for the same promise. Keep the direct PostgreSQL bootstrap behavior and its runtime dependency explicit.

Why not in #43

#43 adds release plumbing and relocates existing README sections; it did not introduce the PostgreSQL bootstrap design. Resolving the product/documentation contract belongs in a focused follow-up.

Acceptance criteria

• Public documentation no longer describes the whole CLI as zero-dependency while postgres ships in its runtime dependencies.
• facility instance bootstrap remains documented as connecting directly to PostgreSQL.
• Package metadata and CLI documentation describe the same runtime requirements.

Start with the “zero-dependency” claim in README.md, then compare packages/cli/package.json with packages/cli/src/instance.mjs and apps/docs/docs/self-host/authentication.md. Audit the public CLI and package documentation for the same wording. Done means the docs state the PostgreSQL runtime requirement, preserve the direct bootstrap connection guidance, and match the package metadata.