feat(sdk+cli): bridge peer — forward a topic between two meshes

A bridge holds memberships in two meshes and relays messages on a
single topic between them. Federation-lite without a broker-to-broker
protocol.

SDK additions:
- Bridge class (start, stop, EventEmitter for forwarded/dropped/error)
- MeshClient.joinTopic / leaveTopic / createTopic methods
- Loop prevention: plaintext hop counter prefix __cmh<n>: with maxHops
  default 2; echo guard via senderPubkey == own session pubkey

CLI additions:
- claudemesh bridge run <config.yaml> long-lived process
- claudemesh bridge init prints config template
- Zero-dep YAML parser for the flat bridge config shape

The hop prefix is visible in message bodies — minor wart, fixed in
v0.3.0 by moving loop tracking into broker primitives.

SDK kept as devDependency since Bun bundles it into dist; no impact
on npm publish or runtime resolution.

Spec: .artifacts/specs/2026-05-02-v0.2.0-scope.md

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/cli/package.json

@@ -55,6 +55,7 @@
     "zod": "4.1.13"
   },
   "devDependencies": {
+    "@claudemesh/sdk": "workspace:*",
     "@turbostarter/eslint-config": "workspace:*",
     "@turbostarter/prettier-config": "workspace:*",
     "@turbostarter/tsconfig": "workspace:*",