fix!: isolate Axios from native and shared runtime imports

[urbankrepel-povio]

Native consumers still needed Axios despite its optional peer metadata: the root entry point eagerly re-exported the Axios client, and shared REST utility declarations imported Axios types. Importing the built root with Axios unavailable reproduced the runtime failure.

Confine Axios-specific exports to /axios and remove Axios types from shared utilities. Message matching accepts unknown errors; filename extraction supports native Headers and Axios-style records. Add an isolated published-artifact consumer check to CI that imports non-Axios entry points and compiles declarations with skipLibCheck disabled without Axios, then verifies the Axios entry point with Axios installed.

Breaking change: move root imports of RestClient, RestInterceptor, RequestInfo, RequestConfig, Response, and IRestClient to @povio/openapi-codegen-cli/axios. NativeRestClient and shared helpers remain available from the root. The README documents this migration.

Local validation:

• Typecheck and lint passed.
• Full TypeScript and required-native suites: 791 passed, 13 skipped each.
• Built artifact runtime and declaration checks passed without Axios; /axios failed as expected when blocked and passed when installed.
• Tree-shaking checks and git diff --check passed.

CI results are separate from these local checks.