docs: explain Connector use and repository ownership

[Raphjacksun7]

Purpose

Turn the repository README into a usable guide for installing the Relay Connector, publishing two named buses, understanding component responsibilities, configuring transport behavior, and handling credentials and failures.

Product result

A Rust developer can identify the available Connector, see its complete declaration, and understand why provider transport code remains outside Core.

Architecture

Documentation only. Core owns capture and Session delivery; the Connector owns Relay client behavior; Relay owns server-side media forwarding.

Verification

• cargo fmt --all -- --check
• cargo test --workspace --all-targets --all-features --locked
• cargo clippy --workspace --all-targets --all-features --locked -- -D warnings
• local links, Markdown fences, and git diff checks

Remaining limits

Connector version 0.1 supports STUN configuration but not TURN credentials. Published proof does not cover every NAT topology or production load.

Scaffold inventory: n/a
Decision: PASS