feat(parser): Add automatic delimiter and header detection

[hat0uma]

Summary

Implements comprehensive CSV dialect detection with automatic delimiter detection, quote character detection, and header row identification.

Key Features

Auto-detect Delimiter

Command-line

" For unknown file formats, let auto-detection work
:CsvViewEnable

Configurations

-- Default configuration with auto-detection
{
  parser = {
    delimiter = {
      ft = {
        csv = ",",        -- Always use comma for .csv files
        tsv = "\t",       -- Always use tab for .tsv files
      },
      fallbacks = {       -- Try these delimiters in order for other files
        ",",              -- Comma (most common)
        "\t",             -- Tab
        ";",              -- Semicolon
        "|",              -- Pipe
        ":",              -- Colon
        " ",              -- Space
      },
    },
  },
}

How Auto-Detection Works

1. If the file type matches ft rules (e.g., .csv → comma), use that delimiter
2. Otherwise, test each delimiter in fallbacks order
3. Score each delimiter based on field consistency across lines
4. Select the delimiter with the highest score

Auto-detect Header

Command-line Header Options

:CsvViewEnable header_lnum=auto  " Auto-detect header (default)
:CsvViewEnable header_lnum=1     " First line as header
:CsvViewEnable header_lnum=none  " No header line

Configurations

-- Default configuration with auto-detection
{
  view = {
    header_lnum = true,  -- Auto-detect header (default)
    sticky_header = {
      enabled = true,
      separator = "─",  -- Separator line character
    },
  },
}

How Header Auto-Detection Works

1. Find the first non-comment line as header candidate
2. Analyze each column independently using two heuristics:
   • Type Mismatch: If the first row contains text while data rows are numeric, it's likely a header
   • Length Deviation: If the first row's text length differs significantly from data rows, it's likely a header
3. Combine evidence from all columns to make the final decision