fix(graphql): send a default User-Agent on tool invocations

[gkze]

GraphQL introspection sets User-Agent: executor-graphql, but query and mutation requests omit an explicit User-Agent. Upstreams that require this header can therefore accept introspection and reject tool calls on runtimes that supply no default.

Set the same default on invocation before applying resolved headers. Caller-provided User-Agent values still override it case-insensitively; other static and authentication headers are unchanged. OpenAPI already uses this ordering.

Validation:

• Regression failed before the fix: invocation inherited Node's node User-Agent rather than the explicit GraphQL default.
• GraphQL package: 123 tests passed, including introspection/query/mutation header coverage and three custom header casing variants.
• Selfhost API-to-sandbox end-to-end scenario passed for default and custom User-Agent, verified against outbound request headers.
• GraphQL package typecheck, scoped lint, formatting and git diff --check passed.

This is a transport fix; no authentication, stored integration, or deployment changes. Full monorepo gates and production validation have not run. The e2e is API-only, so it produces a result artifact rather than a browser recording.

[RhysSullivan]

We're clearing the backlog ahead of the v2 launch, so we're closing this. If it still applies to v2, please open a new issue or PR against v2.

Sent from my Claude