refactor(8.0): drop strictConfig — surface too small to justify the option (scaffold step 9)

Per user direction: after the step-8 simplification reduced
`config.vector` to three knobs (`recall`, `quantization`, `persistMode`),
the `strictConfig` field's only remaining job was warning about
`quantization.bits` being silently ignored on the cortex DiskANN path —
one mismatch case across the entire public surface.

That's not enough surface to justify a declared-but-undelivered config
field. Cleaner to drop it now; if 8.x or 9.0 adds enough provider-knob
mismatch cases to warrant a general-purpose strictness flag, we can add
it back then.

CHANGES

src/types/brainy.types.ts
- Removed BrainyConfig.strictConfig field + its JSDoc block.
- Removed the `strictConfig: 'warn' flags this at init time` reference
  from quantization JSDoc; replaced with a plain "silently ignored on
  DiskANN" note (cortex's B.4 contract still applies).

src/brainy.ts
- normalizeConfig() no longer emits a strictConfig field.

NO-OP scope

Field was declared but had no enforcement logic. Removing it is a pure
type-surface change. No behaviour change.

VERIFICATION

- npx tsc --noEmit: clean
- npm test: 1408 / 1409 (same pre-existing race-condition outstanding)

src/brainy.ts

@@ -9289,9 +9289,6 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       // { except: [...] }: strict, but listed types may omit subtype.
       // Becomes the default in 8.0.0.
       requireSubtype: config?.requireSubtype ?? false,
-      // Provider-knob mismatch strictness (8.0). Default is 'warn' (one-shot
-      // teaching message). See BRAINY-8.0-RENAME-COORDINATION § B.6.
-      strictConfig: config?.strictConfig ?? 'warn',
       // Multi-process safety
       mode: config?.mode ?? 'writer',
       force: config?.force ?? false