Consolidate the non-themes backlog into docs/side-quest-backlog.md: an
exhaustive, deduplicated index compiled from every framing doc's
"Deferred (named)" section, the handoff §6 list, the roadmap arcs, and a
code-level marker sweep. Organized as side quests (one-shot-ish, led by
the highlighting/detection/LSP/editing families that continue the
#114–#118 stack), raid bosses (vterm, folding, DAP, GPU splits, Jupyter),
cross-cutting substrate blockers, and a prioritization north star.
Themes/faces/color items are excluded (they're the Arc 4 main quest) and
listed once so they're visibly accounted for. Handoff §6 gains a pointer
to it.
Docs only. git diff --check clean.
