fix(graphile-schema): replace deepmerge with native preset composition to fix stack overflow

[pyramation]

Summary

buildSchemaSDL used deepmerge to combine the base Graphile preset with caller-provided options. deepmerge recursively clones every nested object — including the pg Pool (EventEmitter internals) and the entire PostGraphile preset tree — which overflows the call stack ("Maximum call stack size exceeded") whenever any graphile option is passed, even {}.

The fix replaces deepmerge with Graphile's native extends mechanism to compose presets, and removes deepmerge as a dependency.

Before:

const preset = opts.graphile
  ? deepmerge(basePreset, opts.graphile)  // 💥 stack overflow
  : basePreset

After:

const preset = {
  extends: [ConstructivePreset, ...(opts.graphile?.extends ?? [])],
  plugins: opts.graphile?.plugins ?? [],
  pgServices: [ ... ],
}

Review & Testing Checklist for Human

• Verify no caller passes preset keys beyond extends/plugins in opts.graphile. The old deepmerge forwarded all keys; the new code only forwards extends and plugins. If any call site passes e.g. disablePlugins, gather, schema, or other preset properties, they'll be silently dropped. Grep for buildSchemaSDL across constructive-db and constructive-hub.
• Re-run the failing CI job (constructive-hub #68664351085) after publishing the updated graphile-schema to confirm all 7 API schema generations succeed end-to-end.
• Confirm the pnpm-lock.yaml diff is only reformatting + deepmerge removal (no unintended dependency changes).

Notes

• Reproduced locally: buildSchemaSDL({ database, schemas, graphile: {} }) overflows; without the graphile key it succeeds. Confirmed the fix resolves all test cases (0 node types through 52 node types).
• The lock file diff is large due to pnpm reformatting resolution fields from multi-line to single-line — no functional dependency changes beyond removing deepmerge.

Link to Devin session: https://app.devin.ai/sessions/6c7e6bf137a34786827fc77a43a7a84a
Requested by: @pyramation

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring