Decouple conflict-helper runbook URL from fold

[c0da-ricon]

notes should remain independent of fold, but packages/notes/lib/conflicts.sh currently hardcodes:

NOTES_CONFLICT_RESOLUTION_URL="https://github.com/ricon-family/fold/blob/main/notes/resolving-encrypted-notes-merge-conflicts.md"

That is useful operator guidance for our current homes, but it couples the package to one private/shared knowledge repo and makes the generic tool look fold-specific.

Requested shape:

• keep hooks and conflict helpers repo-generic;
• move fold-specific runbook links into repo-local config, documentation, or a default message that does not require fold access;
• if a URL is configurable, let fold opt into its runbook while other notes users get generic instructions.

This came up while checking whether notes git hooks had any fold-specific knowledge after a fold branch-switch stale-readable incident.