Booleanish query params spec as anyOf-const unions and degrade to value-swallowing string flags (spec/back-end)

**Behavior:** seven query params (`mine`, `archived`, `effective`, `ignoreWarnings`, `skipSchemaValidation`, `skipPagination`, `overrideDraftLimit`) are speced as the Zod-booleanish union `anyOf: [const 'true', const 'false', const '0', const '1', boolean]`, which the generator degrades to a STRING flag. A bare `--effective --dry-run` silently swallows `--dry-run` as its value and sends `?effective=--dry-run` (server 400) — `--dry-run`/`--debug` "vanish".

**Carried fix:** overlay retypes all seven to plain `type: boolean` (PR #48), making them real switches. The server's booleanish coercion accepts `true`/`false` on the wire either way.

**Retire when:** the back-end Zod→OpenAPI generator emits `type: boolean` for booleanish query params at source (growthbook repo fix), after which the overlay entries can be dropped.

Review the booleanish query-parameter overlay and PR #48, focusing on the seven named flags and how the generated spec represents them. Verify that bare flags such as --effective no longer consume the following option and that true/false values are sent correctly; the longer-term done state is a generator emitting type: boolean so the overlay can be removed.

Written by the indexing model from the issue text.