docs(sandbox): specs for goose harness + GUI distros, command ref, themes

Add the goose-harness and sandbox-distros-GUI design specs, a consolidated
command reference and demo-reels plan, the AI-harness planning note, and
two new client themes (blue-orange, pink-red-gray).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hh/themes/blue-orange.toml

@@ -0,0 +1,13 @@
+name = "blue-orange"
+border = "#425C68"
+title = "#FB8047"
+accent = "#FB8047"
+dim = "#5F7883"
+me = "#ECD0C4"
+other = "#91C2D9"
+system = "#80A9BC"
+input = "#ECD0C4"
+roster_me = "#FB8047"
+bg = "#344E5B"
+roster_width = 22
+sigil = "✟"