fix(appkit): allow undefined values in IGenieConfig.spaces

[jamesbroadhead]

Why

IGenieConfig.spaces is currently typed as Record<string, string>, but the plugin's runtime contract is already permissive of undefined values. defaultSpaces() constructs the same map and freely returns {} when the env var is unset:

private defaultSpaces(): Record<string, string> {
  const spaceId = process.env.DATABRICKS_GENIE_SPACE_ID;
  return spaceId ? { default: spaceId } : {};
}

private resolveSpaceId(alias: string): string | null {
  return this.config.spaces?.[alias] ?? null;
}

When env is unset, spaces.default is undefined at runtime; ?? null coalesces it; routes 404 with "Unknown space alias". That's the intended, working behaviour. The type just doesn't admit it.

The mismatch surfaces the moment a caller wants more than one named alias and reaches for the env var directly:

genie({ spaces: { wanderbricks: process.env.DATABRICKS_GENIE_SPACE_ID } })

error TS2322: Type 'string | undefined' is not assignable to type 'string'.
  Type 'undefined' is not assignable to type 'string'.

The workarounds (?? '', as string, hoist-and-narrow with a runtime throw) all paper over a type that's stricter than the code it describes.

Change

spaces?: Record<string, string> → spaces?: Record<string, string | undefined>. defaultSpaces() return type updated to match. resolveSpaceId is unchanged — ?? null already handles undefined values identically to missing keys.

Alternatives considered

• Require callers to hoist + assert. Three lines per usage to fight a type that doesn't reflect the runtime. Rejected — perpetuates the lie.
• Document as string in the README. Type assertions silently mask config bugs at the callsite without changing runtime behaviour. Rejected — same hazard, less honest.
• Make spaces keys string and require non-empty values via Zod. Real validation, but a strictly bigger change and arguably the wrong layer — the plugin already returns 404 on miss, which is the validation step.

Compatibility

Non-breaking. Function parameter types of Record<K, T> are contravariant for callers: existing callers passing Record<string, string> (a stricter map) still satisfy Record<string, string | undefined> (a looser map). resolveSpaceId's string | null return is unchanged.

Test plan

• pnpm -r typecheck passes
• npx vitest run packages/appkit/src/plugins/genie/tests/genie.test.ts — 30 passed, includes a new test asserting an explicitly-undefined alias 404s the same as a missing key
• npx biome check on touched files — clean
• pnpm build — appkit + appkit-ui rebuild green

This pull request and its description were written by Isaac.