Docs: move point-in-time records to exploration/, trim build-narration, lift open items to plan

docs/exploration/README.md

@@ -0,0 +1,18 @@
+# docs/exploration
+
+Point-in-time records: research, tool reviews, and scope/planning memos written to think a
+decision through. Unlike `docs/spec/` (the contract — the _what_) and `docs/architecture/`
+(the maintained _how_), nothing here is kept current — each file reflects what was known
+when it was written. Decisions that survived are folded into the spec and architecture;
+these remain as the reasoning behind them.
+
+Active follow-up work is tracked in [`../IMPLEMENTATION-PLAN.md`](../IMPLEMENTATION-PLAN.md),
+not here. Exact figures in these files (timings, line counts, test counts) are frozen
+snapshots, not live numbers.
+
+- `chart-builder-research.md` — cross-source chart-choice research (Draco, Voyager, FT Visual Vocabulary, Datawrapper).
+- `lyra-review.md` — review of vega/lyra for Chart Builder interaction ideas.
+- `chart-builder-enhancement-scope.md` — consolidated Tier-B → Tier-C forward plan for the Chart Builder.
+- `chart-theming-scope.md` — chart theming plan and slice breakdown.
+- `monetization-and-sync-exploration.md` — monetization + BYO-cloud-sync direction memo.
+- `data-inspector-exploration.md` — transform-aware data-inspector direction.