Handle schema reopen flows in local consumers

[sorenbs]

Summary

• teach the local package smoke consumers to read /_schema and skip duplicate first-schema installs on reopen
• add a local server regression covering fresh install, restart, registry read, and continued appends
• document the reopen-safe first-schema pattern in schema and release docs

Verification

• bun test test/local_server.test.ts --timeout 30000
• bun run test:node-local-package
• bun run test:bun-local-package
• bun run typecheck

Notes

• this is a follow-up for a consumer-reported 0.1.3 reopen regression