[codex] Fix README accuracy and enable Worker logs

[gharibyan]

Summary

• Clarify README runtime behavior and align bot/search crawler lists with the implementation.
• Add Wrangler observability config to persist Worker logs and invocation logs while leaving traces disabled.
• Add the same observability block to generated Cloudflare project configs.
• Add a root npm tail script and generated README guidance for live log streaming.

Validation

• npm test
• npm run typecheck
• git diff --check
• root observability JSON assertion
• generated scaffold observability JSON assertion
• staged secret/local-path grep returned no matches

Note

• Wrangler dry-run could not run in this local shell because Wrangler 4.97.0 requires Node 22 and this shell has Node 20.12.2. The observability fields were checked against Wrangler's installed config schema.