Export waveforms as TXT and VCD from BeWavedDolphin

[darktorres]

Description

Add export options to BeWavedDolphin for industry-standard waveform formats:

• TXT: Human-readable tabular format
• VCD (Value Change Dump): Compatible with GTKWave, ModelSim, and other waveform viewers

Acceptance Criteria

• Export preserves timing information accurately
• VCD files open correctly in GTKWave and ModelSim
• Preview available before export
• Export accessible from File menu and toolbar

Implementation Guide

1. VCD format

• VCD is a simple text format defined by IEEE 1364 (Verilog standard)
• Structure: header (date, version, timescale) → variable definitions → value changes
• Map each signal row to a VCD variable with a short identifier
• Write only value changes (not every timestep) for compact output
• Timescale: map simulation ticks to a configurable time unit (e.g., 1ns)

2. TXT format

• Header row: signal names tab-separated
• Data rows: one per timestep, values tab-separated
• Include a timestamp column
• Optional: hex/decimal for grouped signals

3. Export UI

• Add File → "Export as VCD..." and "Export as TXT..." to BeWavedDolphin menu
• Preview dialog showing the first N lines of output
• Options: time range selection, signal filtering

4. Implementation

• Add methods to Serializer class: exportVCD(const QString &path), exportTXT(const QString &path)
• Read data from SignalModel rows and columns
• Write using QTextStream for both formats

Key files

• App/BeWavedDolphin/Serializer.h/.cpp — add export methods
• App/BeWavedDolphin/SignalModel.h/.cpp — signal data source
• App/BeWavedDolphin/BeWavedDolphin.cpp — menu actions