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.

COLUMN_ALIGNMENT_VALIDATION.md

@@ -0,0 +1,78 @@
+# Column Alignment Validation
+
+## Expected Column Alignment
+
+The following shows the exact character positions for column alignment:
+
+```
+Position:  123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890
+Header:     #  Source             Proto  Destination        Extended   Frame Type   Pkts  Volume  Timing   Quality
+Flow:       1  192.168.4.89:1024  UDP    239.1.2.10:8080   3 types    Mixed        1452    1.9MB   77.8ms Enhanced
+Sub-row:                                                  CH10       CH10-Data    1110  1.44MB    102ms    76.4%
+Sub-row:                                                  CH10       TMATS         114   148KB    990ms     7.8%
+Sub-row:                                                             UDP           228   296KB    493ms    15.7%
+```
+
+### Right-Aligned Column Validation
+
+The following columns should align on their right edges:
+- **Pkts**: Right edge at position 77
+- **Volume**: Right edge at position 85  
+- **Timing**: Right edge at position 93
+- **Quality**: Right edge at position 101
+
+Example with proper right alignment:
+```
+Pkts Column (6 chars, right-aligned):
+  1452
+  1110
+   114
+   228
+
+Volume Column (8 chars, right-aligned):  
+   1.9MB
+  1.44MB
+   148KB
+   296KB
+
+Timing Column (8 chars, right-aligned):
+  77.8ms
+   102ms
+   990ms
+   493ms
+
+Quality Column (8 chars, right-aligned):
+Enhanced
+   76.4%
+    7.8%
+   15.7%
+```
+
+## Column Specifications
+
+1. **Flow Number**: Positions 1-3 (right-aligned in 2 chars + 1 space)
+2. **Source**: Positions 4-23 (20 characters, left-aligned)
+3. **Proto**: Positions 24-29 (6 characters, left-aligned)
+4. **Destination**: Positions 30-49 (20 characters, left-aligned)
+5. **Extended**: Positions 50-59 (10 characters, left-aligned)
+6. **Frame Type**: Positions 60-71 (12 characters, left-aligned)
+7. **Pkts**: Positions 72-77 (6 characters, right-aligned)
+8. **Volume**: Positions 78-85 (8 characters, right-aligned)
+9. **Timing**: Positions 86-93 (8 characters, right-aligned)
+10. **Quality**: Positions 94-101 (8 characters, right-aligned)
+
+## Sub-Row Alignment
+
+Sub-rows use:
+- Positions 1-3: Empty spaces (matching flow number space)
+- Positions 4-23: Empty (inherits source from main flow)
+- Positions 24-29: Empty (inherits protocol from main flow)  
+- Positions 30-49: Empty (inherits destination from main flow)
+- Positions 50-59: Extended protocol
+- Positions 60-71: Frame type
+- Positions 72-77: Packet count (right-aligned)
+- Positions 78-85: Volume (right-aligned)
+- Positions 86-93: Timing (right-aligned)
+- Positions 94-101: Percentage (right-aligned)
+
+This ensures perfect column alignment between main flow lines and their sub-rows.