feat: reveal all hidden shapes with Shift+H, release SAM3 VRAM on idle and on demand (REQ-191, REQ-192)

docs/ui-spec.md

@@ -201,7 +201,9 @@ falling back to `route.projectId` and then `1`:
 ```
 GPU: <name, stripped of "NVIDIA GeForce" / "Laptop GPU">   |  CPU if none
 VRAM: <free>GB                                             |  N/A
-SAM3: Ready | Off      ← green when ready
+SAM3: Loaded | Idle | Off   ← Loaded = green button, click frees the VRAM (REQ-192)
+                              Idle = green, not in VRAM, loads on next use (~12 s)
+                              Off = not enough free VRAM to load
 ```
 
 Icons are SVG (Heroicons/Lucide-style), never emoji. *(Some emoji survive inside page bodies —
@@ -1171,6 +1173,7 @@ Handlers are attached in the **capture** phase on `document`, and:
 | `1`–`9` | set active class; reclass the selected shape if any | reclass **all marked** shapes |
 | `Del` / `Backspace` | delete the selected shape | delete **all marked** shapes (confirmed) |
 | `H` | hide/show the selected shape(s); no-op with nothing selected | same |
+| `Shift`+`H` | toggle the reveal-all overlay — draws every hidden shape without touching the hidden state; a plain `H` while it is on just turns it off | same |
 | `Esc` | cancel the gesture in flight | clear the marked set |
 | hold `S` | SAM3 assist mode while held | — |
 | `Enter` | apply the exemplar preview (panel open) | — |
@@ -1213,7 +1216,9 @@ network.
   hide; click still selects it and the trash still deletes it. Empty means the frame has
   **zero shapes**, not zero visible ones: *"None on this frame — drag to draw a shape."*
   plus, if the batch has shapes elsewhere, a *Jump to Frame with Shapes [N]* button.
-- **Shortcuts** — a static `<dl>` of the keyboard map (it also lists `H`). Keep it visible;
+  While the reveal-all overlay is on (REQ-191), the header carries a small `revealing hidden`
+  chip — accent-coloured pill, SVG eye icon, `title` explaining `Shift+H` turns it off.
+- **Shortcuts** — a static `<dl>` of the keyboard map (it also lists `H` and `Shift`+`H`). Keep it visible;
   this is a keyboard-first screen and the panel is the discovery mechanism.
 
 ---
@@ -1554,7 +1559,8 @@ di-deep-link — jangan dihapus.
 ### Shell
 
 Top bar tetap 48 px: wordmark kiri → nav urut pipeline di tengah → kanan badge health
-(`GPU: …`, `VRAM: … GB`, `SAM3: Ready/Off` hijau saat siap, polling 3 detik) + toggle tema.
+(`GPU: …`, `VRAM: … GB`, `SAM3: Loaded/Idle/Off` — `Loaded` hijau dan bisa diklik untuk
+melepas VRAM (REQ-192), polling 3 detik) + toggle tema.
 Error boundary membungkus area halaman, di-key per rute.
 
 ### Design token sekarang (boleh diganti, maknanya harus bertahan)