fix(http): falsy ClientRequest method defaults to GET instead of throwing (#4970)

[proggeramlug]

Fixes #4970.

Problem

new ClientRequest({ method: '' }) threw TypeError [ERR_INVALID_HTTP_TOKEN]: Method must be a valid HTTP token [""]. Node only token-validates a truthy method string (if (methodIsString && method) in lib/_http_client.js); a falsy method ('', undefined, null) falls through to the 'GET' default. The #4907 validation over-fired on the empty string, regressing test-http-client-defaults (which #4904 had fixed).

Fix

• crates/perry-ext-http/src/validation.rs — validate_client_options skips the HTTP-token check for an empty method string. A non-empty invalid token (e.g. '\0', 'B@D') still throws ERR_INVALID_HTTP_TOKEN with the same message.
• crates/perry-ext-http/src/lib.rs — method_from_options treats '' as absent → 'GET', so every client path (http.request, http.get, the overload entry points, new ClientRequest) defaults uniformly; the now-redundant empty-method patch-up in js_http_client_request_standalone_new is removed.

Verification

All compiled with the patched binary via perry compile from the workspace root (auto-optimize, ext-http linked), staged with the test-compat/node-core/shim common:

• test-http-client-defaults.js (Node v22 test/parallel) — runtime-fail → pass (exit 0)
• test-http-request-invalid-method-error.js — still pass (method: '\0' is non-empty → still throws, exact message preserved); no re-break of node:http: missing argument/header/URL validation (assert.throws → Missing expected exception) #4907
• Local repro (method: ''/undefined/absent → 'GET', 'B@D' → ERR_INVALID_HTTP_TOKEN, 'post' → 'POST') matches node --experimental-strip-types byte-for-byte
• cargo fmt --check and the 2000-line file-size gate are green

Code-only PR — no version bump / changelog (maintainer folds metadata at merge).