feat(cli): materialize user iii config

[wbugitlab1]

Summary

• materialize the native iii config at ~/.agentmemory/config/iii-config.yaml from the bundled template
• rewrite bundled ./data/state_store.db and ./data/stream_store markers to absolute resolved data-dir paths
• preserve env, project-local, and legacy ~/.agentmemory/iii-config.yaml precedence, including init-time legacy short-circuit
• document the generated config path and add focused temp-home tests

Fixes #503.

Verification

• corepack pnpm exec vitest run test/build-runtime.test.ts test/cli-iii-config.test.ts test/cli-server-log.test.ts test/runtime-config.test.ts test/engine-launch.test.ts --exclude test/integration.test.ts
• corepack pnpm run lint
• corepack pnpm test
• corepack pnpm run build
• semgrep scan --config p/default --error --metrics=off .
• gitleaks protect --staged --redact