feat(windows): icon, windowed exe, no-admin installer

- PyInstaller exe built windowed (console=False) with package/testium.ico
  as the embedded icon (BMP entries for shell compatibility).
- Suppress stray subprocess console windows in the frozen Windows build via
  paths.no_window_kwargs() (CREATE_NO_WINDOW); wheel/source unchanged.
  Applied to py_process, lua_process, bins probes, sys_app_path_win.
- New per-user Inno Setup installer (package/innosetup/): no admin,
  version-scoped AppId/dir so versions install side-by-side, one Start
  Menu entry per version, .ico shipped for shortcut/uninstall icons.
- DESIGN.md + release_note.txt updated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package/innosetup/testium.iss

@@ -0,0 +1,127 @@
+; Inno Setup script: wraps the PyInstaller testium.exe into a per-user installer.
+; Build with Inno Setup 6: ISCC.exe testium.iss (or ./build.ps1).
+
+#define MyAppName "Testium"
+#define MyAppExeName "testium.exe"
+#define MyAppPublisher "Testium"
+#define MyAppURL "https://github.com/"
+
+; Read version from src/VERSION so the installer never drifts from the build.
+#define VerFile FileOpen("..\..\src\VERSION")
+#define MyAppVersion Trim(FileRead(VerFile))
+#expr FileClose(VerFile)
+#if MyAppVersion == ""
+  #error Could not read version from ..\..\src\VERSION
+#endif
+
+[Setup]
+; Version-scoped AppId: each version is a distinct app, installable side-by-side.
+AppId={{B7E6F1C2-9A4D-4E3B-8F71-7C2D5A6E0B14}_{#MyAppVersion}
+AppName={#MyAppName} {#MyAppVersion}
+AppVerName={#MyAppName} {#MyAppVersion}
+AppVersion={#MyAppVersion}
+AppPublisher={#MyAppPublisher}
+AppPublisherURL={#MyAppURL}
+UninstallDisplayName={#MyAppName} {#MyAppVersion}
+WizardStyle=modern
+; Per-version install dir so versions never overwrite each other.
+DefaultDirName={autopf}\{#MyAppName}\{#MyAppVersion}
+; Shared "Testium" Start Menu folder; shortcuts below are named per version.
+DefaultGroupName={#MyAppName}
+UninstallDisplayIcon={app}\testium.ico
+DisableProgramGroupPage=yes
+; Per-user install, no admin ever: installs under %LOCALAPPDATA%, no UAC prompt.
+PrivilegesRequired=lowest
+ArchitecturesInstallIn64BitMode=x64compatible
+OutputDir=dist
+OutputBaseFilename=testium-{#MyAppVersion}-setup
+SetupIconFile=..\testium.ico
+Compression=lzma2/max
+SolidCompression=yes
+; Tell Explorer to refresh the environment after a PATH change.
+ChangesEnvironment=yes
+
+[Languages]
+Name: "french"; MessagesFile: "compiler:Languages\French.isl"
+Name: "english"; MessagesFile: "compiler:Default.isl"
+
+[Tasks]
+Name: "desktopicon"; Description: "{cm:CreateDesktopIcon}"; GroupDescription: "{cm:AdditionalIcons}"; Flags: unchecked
+; PATH off by default: the exe is windowed (console=False), so CLI shows no output.
+Name: "addtopath"; Description: "Ajouter Testium au PATH (usage en ligne de commande)"; Flags: unchecked
+
+[Files]
+Source: "..\pyinstaller\dist\{#MyAppExeName}"; DestDir: "{app}"; Flags: ignoreversion
+; Ship the .ico so shortcuts/uninstall reference it directly, not the embedded one.
+Source: "..\testium.ico"; DestDir: "{app}"; Flags: ignoreversion
+
+[Icons]
+; Per-version names so each install shows separately in the Start Menu.
+Name: "{group}\{#MyAppName} {#MyAppVersion}"; Filename: "{app}\{#MyAppExeName}"; IconFilename: "{app}\testium.ico"
+Name: "{group}\{cm:UninstallProgram,{#MyAppName} {#MyAppVersion}}"; Filename: "{uninstallexe}"
+Name: "{autodesktop}\{#MyAppName} {#MyAppVersion}"; Filename: "{app}\{#MyAppExeName}"; IconFilename: "{app}\testium.ico"; Tasks: desktopicon
+
+[Run]
+Filename: "{app}\{#MyAppExeName}"; Description: "{cm:LaunchProgram,{#MyAppName}}"; Flags: nowait postinstall skipifsilent
+
+[Code]
+const
+  EnvKey = 'Environment';
+
+// True if Param is not already a full segment of the per-user PATH.
+function NeedsAddPath(Param: string): Boolean;
+var
+  OrigPath: string;
+begin
+  if not RegQueryStringValue(HKEY_CURRENT_USER, EnvKey, 'Path', OrigPath) then
+  begin
+    Result := True;
+    exit;
+  end;
+  Result := Pos(';' + Uppercase(Param) + ';', ';' + Uppercase(OrigPath) + ';') = 0;
+end;
+
+// On install: append {app} to the per-user PATH if the task is selected.
+procedure CurStepChanged(CurStep: TSetupStep);
+var
+  Path: string;
+begin
+  if CurStep = ssPostInstall then
+  begin
+    if WizardIsTaskSelected('addtopath') and NeedsAddPath(ExpandConstant('{app}')) then
+    begin
+      if not RegQueryStringValue(HKEY_CURRENT_USER, EnvKey, 'Path', Path) then
+        Path := '';
+      if (Path <> '') and (Copy(Path, Length(Path), 1) <> ';') then
+        Path := Path + ';';
+      Path := Path + ExpandConstant('{app}');
+      RegWriteStringValue(HKEY_CURRENT_USER, EnvKey, 'Path', Path);
+    end;
+  end;
+end;
+
+// On uninstall: strip {app} back out of the per-user PATH.
+procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
+var
+  Path, AppDir, Segment: string;
+  P: Integer;
+begin
+  if CurUninstallStep = usUninstall then
+  begin
+    if RegQueryStringValue(HKEY_CURRENT_USER, EnvKey, 'Path', Path) then
+    begin
+      AppDir := ExpandConstant('{app}');
+      Segment := ';' + AppDir;
+      P := Pos(Uppercase(Segment), Uppercase(Path));
+      if P > 0 then
+        Delete(Path, P, Length(Segment))
+      else
+      begin
+        P := Pos(Uppercase(AppDir) + ';', Uppercase(Path));
+        if P = 1 then
+          Delete(Path, 1, Length(AppDir) + 1);
+      end;
+      RegWriteStringValue(HKEY_CURRENT_USER, EnvKey, 'Path', Path);
+    end;
+  end;
+end;