feat: add MCP server and CLI version flags

[alexeynikandrov]

Summary

• Add an MCP server available through rfc-cli mcp.
• Support MCP initialization over stdio with newline-delimited JSON and Content-Length framing.
• Add read-only tools for listing RFCs, viewing RFC content, checking status, dependencies, and connectivity.
• Automatically configure rfc-cli in .mcp.json during rfc-cli init.
• Add standard --version and -V CLI flags.
• Use the package version from Cargo.toml through clap.
• Add integration tests and documentation for MCP and version output.
• Bump the package version to 0.1.7.
• Complete RFC-0010 and RFC-0011.

Verification

• RFC_VIEWER= make test
• make build
• make release
• cargo fmt -- --check
• cargo clippy -- -D warnings

Verified:

rfc-cli --version
rfc-cli 0.1.7

rfc-cli -V
rfc-cli 0.1.7