BWF Analyser: browser page and macOS app

Reads and edits BWF metadata for production sound. One source tree builds a
single self-contained page and a native Tauri app with a Rust audio engine and
WAV writer. Around 370 checks across seven test suites.

First commit of the existing state, so that from here every change can be
seen and undone.

build/shell.css

@@ -0,0 +1,73 @@
+/* ---------------------------------------------------------------
+   Standalone page shell. The framework above is scoped to
+   .bwfa-scope, so the page around it needs its own few rules.
+   --------------------------------------------------------------- */
+html {
+	-webkit-text-size-adjust: 100%;
+}
+
+body {
+	margin: 0;
+	padding: 0;
+	background: #f4f4f5;
+	color: #18181b;
+	font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
+	font-size: 16px;
+	line-height: 1.5;
+}
+
+.page {
+	max-width: 1500px;
+	margin: 0 auto;
+	padding: 24px 20px 64px;
+}
+
+.page-foot {
+	max-width: 1500px;
+	margin: 0 auto;
+	padding: 0 20px 40px;
+	font-size: 13px;
+	color: #71717a;
+}
+
+.page-foot a {
+	color: #52525b;
+}
+
+.bwfa-scope.bwfa-app {
+	background: #fff;
+	border: 1px solid #e4e4e7;
+	border-radius: 10px;
+	padding: 24px;
+	box-shadow: 0 1px 2px rgba(0, 0, 0, .04);
+}
+
+@media (max-width: 640px) {
+	.page {
+		padding: 12px 10px 48px;
+	}
+
+	.bwfa-scope.bwfa-app {
+		padding: 14px;
+	}
+}
+
+/* Shown only when the browser refuses the folder-write API on file:// */
+.bwfa-fs-warning {
+	display: none;
+	margin: 12px 0 0;
+	padding: 10px 12px;
+	border: 1px solid #f0c36d;
+	background: #fdf6e3;
+	border-radius: 6px;
+	font-size: 13px;
+	line-height: 1.45;
+	color: #6b4e00;
+}
+
+.bwfa-fs-warning code {
+	background: rgba(0, 0, 0, .06);
+	padding: 1px 5px;
+	border-radius: 3px;
+	font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
+}