End-to-end validation of the journey

[swarna1101]

The final gate before closing the parent issue.

• Someone outside the team completes Parts 1 and 2 on a clean machine against prod Console, without asking for help. File fixes for whatever they get stuck on.
• Walk every journey step next to its Console screen and confirm the order and naming match.
• Check that every old URL (live pages plus the /docs/guides/* URLs removed in PR docs: revamp nav around gateway and remove content #40) resolves or redirects.
• Confirm that no journey link points at a pinned gateway version.
• Post the page-by-page disposition list to the Notion audit ticket, and close both Notion tickets.

[linear-code]

OPT-1123