fix(ui): PR #131 review round 2 — manifest cleanup, system index helper, stderr help

Addresses 6 mechanical issues from PR review:

- ImplantAppManifest: drop dead display_name and icon_path fields.
  default_key carries a TODO noting its future migration to a keybinds
  manifest (input concern in app manifest is a layering violation,
  tracked explicitly).
- default_mode wire format is now a String ("fullscreen" / "insert") for
  mod-author discovery. ImplantRegistry parses via _MODE_MAP, caches the
  resolved int in _resolved_modes, and exposes get_resolved_mode(app_path).
  main.gd reads the resolved int directly instead of re-parsing.
- Extract client/ui/implant/widgets/system_index.gd (class_name SystemIndex,
  static get_sorted_systems). Removes duplicated star_map_data.json loader +
  sort lambda from atlas_app and economics overview_screen.
- ImplantApp.on_insert_deactivated() default auto-closes only when the app
  is active in INSERT mode. FULLSCREEN apps no longer spuriously close on
  insert state changes.
- tooling/db/sqlite-query and sqlite-exec: --help output goes to stderr
  (exit 0). Keeps stdout reserved for JSON payloads so JSON-parsing
  callers can't get silently corrupted.

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

client/ui/implant/apps/atlas/app.tres

@@ -5,9 +5,7 @@
 [resource]
 script = ExtResource("1")
 app_path = "implant/map"
-display_name = "ATLAS"
-icon_path = ""
 scene_path = "res://ui/implant/apps/atlas/atlas_app.tscn"
-default_mode = 2
+default_mode = "fullscreen"
 default_key = 77
 preserves_state = true

client/ui/implant/apps/atlas/atlas_app.gd

@@ -6,8 +6,6 @@ extends ImplantApp
 
 signal economics_link_requested(system_id: String)
 
-const STAR_MAP_DATA := "res://data/star_map_data.json"
-
 var _systems: Array = []
 var _system_lookup: Dictionary = {}  # system_id → system dict
 
@@ -193,24 +191,6 @@ func _system_idx_by_id(system_id: String) -> int:
 
 
 func _load_system_data() -> void:
-	if not FileAccess.file_exists(STAR_MAP_DATA):
-		push_warning("AtlasApp: %s not found" % STAR_MAP_DATA)
-		return
-	var file := FileAccess.open(STAR_MAP_DATA, FileAccess.READ)
-	if file == null:
-		return
-	var parsed: Variant = JSON.parse_string(file.get_as_text())
-	file.close()
-	if not (parsed is Dictionary):
-		return
-	for node: Dictionary in parsed.get("nodes", []):
-		var sid: String = node.get("system_id", "")
-		if not sid.is_empty():
-			_systems.append(node)
-			_system_lookup[sid] = node
-	_systems.sort_custom(
-		func(a: Dictionary, b: Dictionary) -> bool:
-			var na: String = a.get("proper_name", a.get("system_id", ""))
-			var nb: String = b.get("proper_name", b.get("system_id", ""))
-			return na < nb
-	)
+	_systems = SystemIndex.get_sorted_systems()
+	for node: Dictionary in _systems:
+		_system_lookup[node.get("system_id", "")] = node

client/ui/implant/apps/economics/app.tres

@@ -5,9 +5,7 @@
 [resource]
 script = ExtResource("1")
 app_path = "implant/economics"
-display_name = "ECONOMICS MONITOR"
-icon_path = ""
 scene_path = "res://ui/implant/apps/economics/economics_app.tscn"
-default_mode = 1
+default_mode = "insert"
 default_key = 78
 preserves_state = true

client/ui/implant/apps/economics/screens/overview_screen.gd

@@ -10,7 +10,6 @@ extends Control
 signal economy_data_updated(system_id: String, data: Dictionary)
 
 const RING_BUFFER_SIZE: int = 20
-const STAR_MAP_DATA := "res://data/star_map_data.json"
 const PANEL_WIDTH: float = 340.0
 const PANEL_MARGIN: float = 16.0
 
@@ -112,26 +111,7 @@ func navigate(delta: int) -> void:
 
 
 func _load_system_list() -> void:
-	if not FileAccess.file_exists(STAR_MAP_DATA):
-		push_warning("OverviewScreen: %s not found" % STAR_MAP_DATA)
-		return
-	var file := FileAccess.open(STAR_MAP_DATA, FileAccess.READ)
-	if file == null:
-		return
-	var parsed: Variant = JSON.parse_string(file.get_as_text())
-	file.close()
-	if not (parsed is Dictionary):
-		return
-	for node: Dictionary in parsed.get("nodes", []):
-		var sid: String = node.get("system_id", "")
-		if not sid.is_empty():
-			_systems.append(node)
-	_systems.sort_custom(
-		func(a: Dictionary, b: Dictionary) -> bool:
-			var na: String = a.get("proper_name", a.get("system_id", ""))
-			var nb: String = b.get("proper_name", b.get("system_id", ""))
-			return na < nb
-	)
+	_systems = SystemIndex.get_sorted_systems()
 	if not _systems.is_empty():
 		selected_system = _systems[0].get("system_id", "")