feat(executor): expose ctx.request.method to scripts (F4)

The request map exposed path/headers/body/params/query/rest but not the
HTTP method, forcing one script per verb (the E2E app needed 7 scripts
where ~3 would do). Add a `method` field to ExecRequest (populated from
the HTTP method on the sync-execute bypass and the HTTP outbox payload;
empty for non-HTTP triggers) and surface it as `ctx.request.method`,
uppercased. A single script can now branch GET/POST on one route.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/executor-core/tests/sdk_pubsub.rs

@@ -65,6 +65,7 @@ fn baseline_request(app_id: AppId) -> ExecRequest {
         script_name: "pubsub-test".into(),
         invocation_type: InvocationType::Http,
         path: "/pubsub-test".into(),
+        method: String::new(),
         headers: BTreeMap::new(),
         body: Value::Null,
         params: BTreeMap::new(),