Docs: audit and remove dev-only URLs (localhost / hubs.local)

## Summary

Some documentation pages still reference dev-only URLs such as `localhost` or `hubs.local`, which do not resolve for readers on the published docs site.

Examples:
- `docs/local-ubuntu-vm-setup.md` (describing access to hubs.local)
- historical references in setup or developer guides

## Motivation

While some mentions may be intentional (e.g. local dev instructions), others appear in user-facing flows where they may be confusing or misleading.

Clarifying which cases are intentional vs accidental would improve documentation clarity.

## Proposed approach

- Identify and list remaining dev-only URL references
- Decide which should:
- remain (explicit local-dev context)
- be replaced with relative or environment-agnostic links
- be clarified with explanatory text

I am not proposing any changes in this issue. I am raising this this is for discussion and triage purposes only.

Search the docs for `localhost` and `hubs.local`, then review `docs/local-ubuntu-vm-setup.md` and the referenced setup or developer guides to classify each mention as intentional or accidental. Done means the remaining references are inventoried and each has an explicit keep, replacement, or clarification decision; the issue does not yet define the resulting edits.

Written by the indexing model from the issue text.