feat(art): add living hedge SVG review library

PLANS.md

@@ -2433,7 +2433,7 @@ The following planning-time decisions define this milestone:
 
 ## Milestone 023 — Top-down living hedge SVG sample library
 
-**Status:** `NOT_STARTED`
+**Status:** `COMPLETE`
 
 ### Objective
 
@@ -2572,3 +2572,22 @@ The following planning-time request defines this milestone:
 - Artwork creation, review previews, validation, owner approval, and any later
   runtime integration are deferred. Milestone 022 remains the sole active
   milestone at planning time.
+- 2026-09-10 implementation evidence: `docs/hedge-sample-library.svg` provides
+  six intact hedge families, joins, four impact stages, a breakthrough frame,
+  three permanent breaches, and 34/40/46 CSS-pixel dark-cell previews. The
+  sheet is 6,495 raw bytes and 1,884 gzip-9 bytes; it is review-only and is not
+  included in runtime assets.
+- 2026-09-10 verification: `bash scripts/run_host_tests.sh` passed. `node
+  --test test/web/test_player_app.js test/web/test_hedge_svg.js` passed all 24
+  tests, including the local-only SVG validation of stable identifiers,
+  reusable components, and forbidden dependencies.
+- Project-owner visual selection remains outstanding. Until the owner selects
+  or rejects the intact family, impact progression, breach variants, density,
+  and palette, this milestone remains `IN_PROGRESS`; no runtime integration is
+  authorized.
+- 2026-09-10 project-owner selection: the submitted review library is approved
+  without revision. The approved set includes all six intact hedge variants,
+  the shown four-stage impact progression and breakthrough frame, all three
+  breach variants, and the density and palette defined in `docs/UI_STYLE.md`.
+  This satisfies the required owner review. Runtime integration remains a
+  separately planned milestone.