Enhanced Textual TUI with proper API usage and documentation

- Fixed DataTable row selection and event handling
- Added explicit column keys to prevent auto-generated keys
- Implemented row-to-flow mapping for reliable selection tracking
- Converted left metrics panel to horizontal top bar
- Fixed all missing FlowStats/EnhancedAnalysisData attributes
- Created comprehensive Textual API documentation in Documentation/textual/
- Added validation checklist to prevent future API mismatches
- Preserved cursor position during data refreshes
- Fixed RowKey type handling and event names

The TUI now properly handles flow selection, displays metrics in a compact top bar,
and correctly correlates selected rows with the details pane.

analyzer/tui/textual/styles/streamlens.tcss

@@ -0,0 +1,148 @@
+/* StreamLens Textual CSS Styling */
+
+/* Main application layout */
+#main-container {
+    height: 1fr;
+    padding: 1;
+}
+
+#status-summary {
+    height: 1;
+    background: $primary;
+    color: $text;
+    text-align: center;
+    margin-bottom: 1;
+}
+
+/* Flow Analysis Tab Styling */
+#flow-title {
+    height: 1;
+    text-align: center;
+    text-style: bold;
+    color: $accent;
+    margin-bottom: 1;
+}
+
+#flows-table {
+    height: 1fr;
+    border: solid $primary;
+}
+
+#flows-table:focus {
+    border: solid $accent;
+}
+
+/* Enhanced flow styling */
+.enhanced-flow {
+    background: $success 50%;
+    color: $text;
+}
+
+/* Packet Decoder 3-panel layout */
+#flow-summary-panel {
+    width: 25%;
+    border: solid $primary;
+    margin-right: 1;
+}
+
+#packet-list-panel {
+    width: 1fr;
+    border: solid $primary;
+    margin-right: 1;
+}
+
+#field-details-panel {
+    width: 25%;
+    border: solid $primary;
+}
+
+#flow-summary-title, #packet-list-title, #field-details-title {
+    height: 1;
+    text-align: center;
+    text-style: bold;
+    color: $accent;
+    background: $surface;
+}
+
+#flow-tree, #packet-table, #field-tree {
+    height: 1fr;
+}
+
+/* Statistics Dashboard */
+#stats-title {
+    height: 1;
+    text-align: center;
+    text-style: bold;
+    color: $accent;
+    margin-bottom: 1;
+}
+
+#metrics-summary {
+    height: 3;
+    margin-bottom: 1;
+}
+
+#metrics-summary Static {
+    width: 1fr;
+    border: solid $primary;
+    margin-right: 1;
+    text-align: center;
+    padding: 1;
+}
+
+#metrics-summary Static:last-child {
+    margin-right: 0;
+}
+
+/* Table styling */
+DataTable {
+    height: 1fr;
+    scrollbar-gutter: stable;
+}
+
+DataTable .even {
+    background: $surface;
+}
+
+DataTable .odd {
+    background: $background;
+}
+
+DataTable .cursor {
+    background: $accent;
+    color: $text;
+}
+
+/* Tree styling */
+Tree {
+    height: 1fr;
+    scrollbar-gutter: stable;
+}
+
+Tree > .tree--label {
+    color: $text;
+}
+
+Tree > .tree--label:hover {
+    background: $primary 30%;
+}
+
+/* General widget styling */
+TabbedContent {
+    height: 1fr;
+}
+
+TabPane {
+    height: 1fr;
+    padding: 1;
+}
+
+/* Color scheme */
+$primary: blue;
+$accent: cyan;
+$success: green;
+$warning: yellow;
+$error: red;
+$surface: grey 20%;
+$background: black;
+$text: white;