fix: add | null to composite type fields in TypeScript generator

[nancysangani]

What kind of change does this PR introduce?

Bug fix

What is the current behavior?

Composite type fields were not emitting | null in the generated TypeScript types, making them incorrectly non-nullable.

Fixes #763

What is the new behavior?

All composite type fields now emit | null, including domain-typed fields which previously fell through to unknown without | null.

Before:

CompositeTypes: {
  t: {
    a: number
    b: unknown
  }
}

After:

CompositeTypes: {
  t: {
    a: number | null
    b: unknown | null
  }
}

Additional context

Per the PostgreSQL docs, composite type fields cannot have NOT NULL constraints, so every field is inherently nullable.

[Copilot]

Pull request overview

Fixes TypeScript type generation for PostgreSQL composite types by ensuring every composite type field is emitted as nullable (| null), including fields whose underlying type resolves to unknown (e.g., domain-typed fields).

Changes:

• Updated the TypeScript template to always append | null to composite type attributes.
• Extended the test database schema with a domain + composite type that uses it.
• Updated TypeScript typegen snapshot expectations to include the new composite type and nullability.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
src/server/templates/typescript.ts	Ensures composite type attributes are emitted as `${tsType}
test/db/00-init.sql	Adds a domain and a composite type using that domain to exercise the domain-as-attribute case.
test/server/typegen.ts	Updates expected generated TS output to include the new composite type and `

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