This pull request introduces dynamic server reflection support to the `granc` CLI, allowing users to call gRPC services without needing a local descriptor file. The changes include new reflection client logic, CLI and core refactoring, an updated README, and build system improvements.
**Server Reflection Support:**
* Added a copy of the official `grpc.reflection.v1` proto file to `granc/proto/reflection.proto` to enable dynamic schema fetching from servers that support reflection.
* Implemented logic in the core orchestration layer (`granc/src/core.rs`) to resolve service descriptors either from a local file or dynamically via server reflection. The CLI now works seamlessly whether or not a `--proto-set` is provided.
**CLI and Core Refactoring:**
* Moved the CLI definition to `granc/src/cli.rs`, now supporting an optional `--proto-set`, improved endpoint parsing, and conversion to the new internal core `Input` type.
* Refactored the core logic into `granc/src/core.rs` and implemented a more structured input, output and error handling, now making the core logic unit testable.
**Documentation and Usability:**
* Updated `granc/README.md` to document the new server reflection feature, clarify usage with and without descriptor files, and revise CLI argument documentation and examples. [[1]](diffhunk://#diff-0648f0ef1e166ae07f3ab14aa268c3497c2e3a49ffa189f85f9dfb88493f2440R17-L19) [[2]](diffhunk://#diff-0648f0ef1e166ae07f3ab14aa268c3497c2e3a49ffa189f85f9dfb88493f2440L34-R44) [[3]](diffhunk://#diff-0648f0ef1e166ae07f3ab14aa268c3497c2e3a49ffa189f85f9dfb88493f2440L57-R101) [[4]](diffhunk://#diff-0648f0ef1e166ae07f3ab14aa268c3497c2e3a49ffa189f85f9dfb88493f2440L97) [[5]](diffhunk://#diff-0648f0ef1e166ae07f3ab14aa268c3497c2e3a49ffa189f85f9dfb88493f2440L106-R125)
**Generating a reflection service:**
* Updated `granc/Cargo.toml` to add a `gen-proto` feature, declare both binaries (`granc` and `generate_reflection_service`), and manage dependencies for reflection and proto generation.
* Improved `Makefile.toml` with new tasks for generating the reflection service client.
