docs: fix stale comments

[jhateley-godaddy]

Related issue

Fixes #60

Summary

Corrects three inaccurate comments in internal/ra/service/lifecycle.go that named event types the code doesn't emit:

• RegisterServerCert doc said it emits AGENT_ACTIVE — it emits AGENT_REGISTERED.
• RevokeInput doc referenced AGENT_REVOCATION — the actual token is AGENT_REVOKED.
• VerifyInput doc claimed V2 emits AGENT_ACTIVE and referenced a non-existent intermediate DOMAIN_VALIDATION event type. Both lanes emit AGENT_REGISTERED at the ACTIVE transition (only the attestation shape
  differs); DOMAIN_VALIDATION is a challenge purpose, not an event type.

Comments only — no behavior change.

Testing

No tests updated - docs fix only

AI assistance

Checklist

• The PR title follows Conventional Commits — release notes are generated from it
• Tests cover the change
• The linked issue above uses a closing keyword
• Every commit is signed off (git commit -s) certifying the DCO

[Copilot]

Pull request overview

This PR updates internal RA documentation comments to match the current lifecycle/event model, removing references to retired event types and clarifying when terminal lifecycle events are emitted.

Changes:

• Update VerifyDNS, RevokeInput, and VerifyInput comments to reference AGENT_REGISTERED / AGENT_REVOKED and the terminal-only emission model.
• Update helper documentation to reflect that metadata hashes are carried on the AGENT_REGISTERED attestation.
• Clarify registration handler commentary about when production DNS records are surfaced (and where they appear in the API).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
internal/ra/service/lifecycle.go	Fixes stale lifecycle comments referencing retired event types and incorrect lane behavior.
internal/ra/service/helpers.go	Updates helper doc to reference the correct attestation/event type.
internal/ra/handler/registration.go	Refines handler docs about when production DNS records become available to clients.

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