Relax source header enforcement for proxy and bridge

Fix provider ownership and session_id placeholder tracing

Enforce session_id source header and add runtime diagnostics

fix: inject session marker only for proxy-targeted requests

Document config.json location in README

Use plugin config.json as single source for proxy port

Support proxy port in config.json with sane precedence

Add configurable proxy port via plugin config

Trim README to installation-focused instructions

Add npm packaging metadata and publish instructions

Initial OpenClaw session ID bridge extension