Troubleshooting page is registered twice in mkdocs.yml and the index #154

Reproduction

main @ 87af91f (merged PR #145) registers the Troubleshooting page twice:

• mkdocs.yml lines 51–52: two identical - Troubleshooting: troubleshooting.md nav entries.
• docs/index.md lines 55–56: two "Where to go next" bullets linking troubleshooting.md with different blurbs.

MkDocs Material renders a duplicated nav section and the index shows two near-identical links.

Expected

One nav entry and one index link for the Troubleshooting page.

Actual

Two of each; the second registration is redundant and the two blurbs disagree in wording.

Impact

Docs-site navigation clutter; confusing "Where to go next" list. No package/runtime impact. Found by Cursor Bugbot's review note on PR #145 and verified against main (2026-10-09).

Acceptance criteria

• mkdocs.yml has exactly one Troubleshooting nav entry.
• docs/index.md has exactly one Troubleshooting bullet in "Where to go next".
• mkdocs build --strict green; npm run lint:llm green.

Context: discovered while selecting the next task from #146 (the docs copy pass, #149, replaces the page set afterward, but the duplicate should not sit on main in the meantime).