refactor: fix error introduced by merge, reorganize features

[4t145]

1. Reorganize features, remove tls related options
2. Make reqwest a non-default dependent, so people can toggle its features theirselves.

Motivation and Context

fix error introduced by merge

How Has This Been Tested?

Breaking Changes

1. rename feature transport-sse => transport-sse-client (it should be done in refactor: Transport trait and worker transport, and streamable http client with those new features. #167, but seems missed due to merge?)
2. make reqwest client an optional choice.
3. simplify tls provider featrues to reqwest and reqwest-tls-no-provider, otherwise there would be too many tls option features.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context

It breaks the changes of #155.
cc @msardara

[Copilot]

Pull Request Overview

This PR refactors feature flags to fix a merge error, streamlines TLS/provider options, and makes reqwest an optional dependency.

• Renamed SSE transport feature (transport-sse → transport-sse-client) and consolidated TLS flags into reqwest and reqwest-tls-no-provider.
• Updated example projects and documentation to use new feature names and bumped reqwest to v0.12.
• Adjusted internal module cfg guards (__auth → auth, __transport-* → new feature names).

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
examples/simple-chat-client/src/config.rs	Switched from SseTransport to SseClientTransport and updated call to start
examples/simple-chat-client/Cargo.toml	Bumped reqwest version; replaced git dependency with workspace = true and updated rmcp features
examples/rig-integration/Cargo.toml	Renamed transport-sse feature to transport-sse-client
examples/clients/Cargo.toml	Renamed transport-sse to transport-sse-client and added reqwest feature
docs/OAUTH_SUPPORT.md	Updated example to use transport-sse-client feature
crates/rmcp/src/transport/streamable_http_client.rs	Changed feature guard from __auth to auth
crates/rmcp/src/transport/sse_client.rs	Removed URL and join error variants; switched to auth guard
crates/rmcp/src/transport/common/reqwest.rs	Aligned feature guard to transport-streamable-http-client
crates/rmcp/src/transport/common/auth.rs	Aligned feature guard to transport-streamable-http-client
crates/rmcp/src/transport/common.rs	Changed reqwest guard to __reqwest
crates/rmcp/src/transport.rs	Updated multiple feature gates for SSE, auth, and streamable HTTP
crates/rmcp/Cargo.toml	Reorganized feature definitions and updated test feature requirements

Comments suppressed due to low confidence (3)

crates/rmcp/src/transport/sse_client.rs:29

• The Url error variant was removed, but parse errors may still occur; reintroduce or properly handle URL parsing failures to avoid unhandled errors or compilation issues.

    #[error("Url error: {0}")]

examples/simple-chat-client/Cargo.toml:16

• [nitpick] Using workspace = true here while other examples use path may lead to inconsistent crate resolution; consider using a consistent path = "../../crates/rmcp" reference for local development.

rmcp = { workspace = true, features = [

crates/rmcp/Cargo.toml:150

• [nitpick] The test required-features now includes __reqwest but not its TLS sub-features; ensure any dependent TLS flags (e.g., rustls-tls) are also enabled if tests exercise HTTP functionality.

    "__reqwest",

[Copilot]

The doc(cfg(...)) annotation references feature = "reqwest" but the guard uses __reqwest, causing a mismatch in generated docs; align the documented feature name with the actual flag.

Suggested change

	#[cfg(feature = "__reqwest")]
	#[cfg(feature = "reqwest")]

[4t145]

It would be bad looking to see an internal feature "__reqwest" in the document.