feat: add copy as grpcurl for gRPC requests

[lucasAguiar11]

What & why

HTTP requests already support Copy as … (cURL, HTTPie, fetch). gRPC had no equivalent export for the terminal.

This PR adds Copy as grpcurl for gRPC tree nodes:

• Plugin API: GrpcRequestActionContribution + grpcRequestActions (typed, not cast from HTTP)
• First-party plugin @voleeo/grpcurl — serializes target, TLS/plaintext, proto files/reflection, message (-d), metadata and auth as -H
• Host inheritance for folder/workspace headers + Inherit auth (same idea as HTTP withInheritedData)
• Context menu: Copy as … → grpcurl on kind === "grpc"

Auth schemes match send-time gRPC resolution (apply_to_grpc): bearer, basic, api_key; HTTP-only schemes are omitted.

Closes #45

How to test

1. Open a gRPC request with target, service, and method set
2. Right-click the node in the tree → Copy as … → grpcurl
3. Paste into a terminal; flags should match the request (plaintext/TLS, protos if files, body, headers)
4. Incomplete request (missing service/method) should not show a broken copy action
5. HTTP Copy as … still works unchanged

Out of scope (v1)

• mTLS flags, streaming multi-message, paste reverse, ⌘C on gRPC, MCP export

Checklist

• bun run typecheck, bun run lint, and the cargo checks pass (see CONTRIBUTING.md)
  • typecheck / lint / frontend tests + bun test plugins/grpcurl run locally; no Rust changes
• New Tauri commands are registered in collect_commands! and bun run codegen was run
  • N/A — no new Tauri commands / codegen
• Follows the rules in AGENTS.md (file-size limits, render-loop rules, no migration shims)