Define observability baseline across Proffer packages

[asiffermann]

Context

Legacy issue #23 requested adding logging. Reactivation reframes this as an observability baseline across all packages.

Scope

• Define minimal logging and diagnostics baseline per package type
• Standardize event names and log levels for core operations
• Document expected telemetry and logging behavior

Notes

Supersedes #23 and #35 in reactivation context.

[asiffermann]

Updated supersession note: this issue supersedes both #23 and #35.