docs: start TODO.md — giftable-tag presentation idea

giftable is a facet, not a topic; parked the idea of giving it a
tasteful prominent surface once the gifts topic migrates to a tag.

Claude-Session: https://claude.ai/code/session_01WZaczDJjL3xZ3u5spsN5AL

TODO.md

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+# TODO
+
+Ideas and deferred work — not a task tracker for in-flight changes.
+
+- **Giftable finds, presented tastefully.** `giftable` is a facet, not a topic
+  (kept off the topics vocabulary by design). Once the `gifts` topic values
+  migrate to a `giftable` tag, revisit giving it a more prominent, tasteful
+  surface — e.g. a curated "gift ideas" view or a seasonal shelf — without
+  turning the site into a gift guide.