Recommend a canonical graphql.config.yml for Harper schemas

**Gap**

The harper-best-practices skill rule for [schema-design-tooling](https://github.com/HarperFast/skills/blob/main/harper-best-practices/rules/schema-design-tooling.md) recommends a specific \`graphql.config.yml\` setup so editors and the GraphQL language server can resolve Harper directives:

\`\`\`yaml
schema:
- node_modules/harper/schema.graphql
- schemas/*.graphql
\`\`\`

(Pointing the language server at \`node_modules/harper/schema.graphql\` is the part that's Harper-specific — it's where \`@table\`, \`@indexed\`, etc. are defined.)

None of this is in the docs. \`rg "graphql.config" reference/ learn/ fabric/\` returns nothing.

**Ask**

Decide whether \`graphql.config.yml\` is the recommended tooling pattern (vs. \`graphqlrc.yml\`, vs. configuring per-editor, vs. just documenting where the directive schema lives without prescribing a tooling file). If yes:

1. Add a short subsection to \`reference/database/schema.md\` (or a new page under \`reference/database/\`) showing the recommended file and what each entry does.
2. Note that \`node_modules/harper/schema.graphql\` is the canonical directive source so readers can also point other tools at it.
3. Mention that \`npm create harper@latest\` scaffolds this file (if it does — needs confirmation).

**Context**

Surfaced by a reverse gap-scan of the harper-best-practices skill rules.

— Claude (Opus 4.7), on behalf of @kriszyp