chore: keep reference photography local and out of the repository

Reference images are development-only material: licensing is not a gate for
local private use, so they are simply never committed. Art/reference/ is now
gitignored; the licensed status of anything shipped is still recorded in
THIRD_PARTY_NOTICES.md.

Adds Tools/commons_fetch.py, which fetches Wikimedia Commons imagery by search
or exact title and writes a provenance sidecar, plus Docs/reference-notes-hollywood.md
recording what each local set is evidence for.

Docs/licensing.md

@@ -12,7 +12,7 @@ Licensing is tracked in four separate layers. Do not merge them; each has differ
 ## Rules
 
 1. An asset whose licence cannot be verified does not get committed. Record it as unresolved in [THIRD_PARTY_NOTICES.md](../THIRD_PARTY_NOTICES.md) and replace it with a redistributable asset before the release it would ship in.
-2. Reference photography is development evidence, not shipped content. Keep it in the repository only when its licence permits redistribution, and state in the notices that it is not built into the game.
+2. Reference photography is dev-only material and is **never committed**. It lives in the gitignored `Art/reference/` tree, is used for internal, private development only, and is not shipped or baked into shipped textures. What the images are evidence for is recorded in [reference-notes-hollywood.md](reference-notes-hollywood.md); the images stay outside version control.
 3. OSM is layout data only. Do not treat it as authoritative for façades, heights, or pavement detail, and do not import it as a texture or panorama source.
 4. Never use extracted Google imagery, Street View, or geometry. No exception.
 5. Attribution: "© OpenStreetMap contributors" with a link to <https://www.openstreetmap.org/copyright> appears in the shipped build's UI (a `0.1.0` release check) and in the notices.
@@ -23,8 +23,8 @@ Licensing is tracked in four separate layers. Do not merge them; each has differ
 - **Code licence.** MIT is proposed: short, compatible with the assets' separate terms, and no copyleft spill onto art. Decide before publishing the repository.
 - **Documentation licence.** Default to the code licence unless a reason appears to separate them.
 - **ODbL posture.** Decide whether distributed builds contain a derived geographic database (a modified OSM extract) or only rendered geometry. The answer changes the share-alike obligations for the shipped product. Record the decision here and in the release notes.
-- **Reference photography retention.** Decided 2026-11-06: the El Capitan reference set is committed under `Art/reference/hollywood/` with its `SIDECAR.md` provenance carried over verbatim, because every file is CC0, public domain, CC BY, or CC BY-SA and none is shipped. The CC BY-SA review note travels with the set. Re-check before any material is derived from a frame.
+- **Reference photography retention.** Decided 2026-11-06: reference images are **not** committed. Licensing is not the gate for local, private development use, so images are simply kept out of the repository (`Art/reference/` is gitignored) and their provenance stays in the local sidecars. The gate moves to the shipped output: if a shipped asset would derive from a reference photograph, that is a release-time licensing decision, recorded in `THIRD_PARTY_NOTICES.md` before the asset ships.
 
 ## Provenance sources
 
-Primary record: [THIRD_PARTY_NOTICES.md](../THIRD_PARTY_NOTICES.md). The sibling project at `…/06-games/security-game/docs/screens/refs/hollywood/SIDECAR.md` holds the original per-file provenance for the El Capitan block photographs; a verbatim copy now lives at `Art/reference/hollywood/SIDECAR.md`.
+Primary record: [THIRD_PARTY_NOTICES.md](../THIRD_PARTY_NOTICES.md) for anything committed or shipped, and [reference-notes-hollywood.md](reference-notes-hollywood.md) for what the local-only reference images are evidence of. Per-file provenance for the local sets lives in `Art/reference/hollywood/SIDECAR.md` and in each folder's `sidecar.json` — local files, not committed.