fix(ui): address PR #115 review — 8 items

- Fix stale test path UILayer/HUD → InsertOverlay/HUD
- Fix D-record citation D-051 → D-049 in main.tscn
- Add null guards to hud.gd update methods (pre-_ready safety)
- Minimap: dirty-flag queue_redraw instead of per-frame
- Remove redundant _panel.size.x, debug print
- Fix DebugOverlay/GauntletHUD positioning comments

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

client/scenes/main.tscn

@@ -144,12 +144,12 @@ layer = 10
 ; #264: Journal panel — knowledge graph review, toggle J key, read-only (D-041)
 [node name="JournalPanel" parent="InsertOverlay" instance=ExtResource("25_journal")]
 
-; HUD — implant-styled status panel (D-169, D-170). On InsertOverlay for bloom per D-051.
+; HUD — implant-styled status panel (D-169, D-170). On InsertOverlay per D-049 (z-layer 6).
 [node name="HUD" parent="InsertOverlay" instance=ExtResource("6_hud")]
 
 ; --- UI layer (CanvasLayer 20) ---
 ; Monologue, cursor, stance — always visible, not affected by fog or camera.
-; HUD moved to InsertOverlay (layer 10) for bloom treatment per D-051.
+; HUD moved to InsertOverlay (layer 10) per D-049 (insert z-layer 6).
 [node name="UILayer" type="CanvasLayer" parent="."]
 layer = 20
 
@@ -168,7 +168,7 @@ layer = 20
 [node name="InventoryGrid" parent="UILayer" instance=ExtResource("12_inv")]
 
 ; #511: F3 debug overlay — real-time game state, toggled by F3
-; Position: below merged HUD status panel (starts at y:16, ~80px), 10px gap
+; Position: y:150 — below merged HUD status panel (y:16, ~80px tall), with gap
 [node name="DebugOverlay" type="Control" parent="UILayer"]
 anchors_preset = 0
 offset_left = 16