feat(roms): add Obsidian vault knowledge base for 75 library romhacks

build-romhack-vault.py generates pokemon-romhack-vault/: one note per hack
(YAML properties + tags + summary + links), an Index MOC (Dataview + static
table), a Types taxonomy, and per-platform MOCs. Dataset is the single source
of truth — edit + re-run to extend.

pokemon-romhack-vault/README.md

@@ -0,0 +1,23 @@
+# Pokémon ROM-Hack Vault
+
+An [Obsidian](https://obsidian.md) vault documenting the **75** Pokémon ROM-hacks
+in the valhalla library. Open *this folder* as a vault (or copy it into an existing one).
+
+## Layout
+- **[[Index]]** — the master directory (Dataview + static table).
+- **[[Types]]** — the type taxonomy (QoL, Vanilla+, Difficulty, Expansion, New Experience, Demake, Roguelite, Cosmetic).
+- **Hacks/** — one note per hack with frontmatter properties + tags.
+- **Platforms/** — per-system maps of content (GBA / GBC / GB / NDS).
+
+## Conventions
+- Frontmatter uses Obsidian **properties** (`platform`, `base`, `version`, `status`, `type`, `generation`, `source`) so the **Dataview** and **Bases** plugins work.
+- Every note also carries **tags** (`#platform/gba`, `#type/difficulty`, `#status/complete`, `#base/firered`) so search/graph work with **zero plugins**.
+- `library_path` points at the file under `roms/<platform>/Hacks/` on valhalla.
+
+## Recommended plugins
+- **Dataview** (the Index/Platform tables) and optionally **Bases** (Obsidian's native DB view).
+
+## Caveats
+- `base`, `version`, and `type` are best-effort from the import metadata + general knowledge; a few obscure hacks show `base: —` where the source wasn't certain. Correct any in `scripts/build-romhack-vault.py` and re-run.
+
+*Generated by `scripts/build-romhack-vault.py`.*