Implement SQL documentation extraction via `sqlparser`

[RPG-Alex]

Summary

Integrate sqlparser and implement a pipeline that parses SQL files, walks the original source text, and associates preceding -- comments with tables and columns for documentation generation.

Processing flow

For each .sql file:

1. Parse SQL statements with sqlparser.

2. For each CREATE TABLE statement:

   • Identify the source text span of the table declaration and its columns.
   • Walk upwards from each table/column line in the original source to collect contiguous preceding -- comments.
   • Stop when a non-comment line is reached.

3. Build structured documentation from those collected comment blocks.

Requirements

• Use sqlparser as the SQL frontend (AST + basic validation).

• Always operate on the original source text to locate comments (don’t rely purely on AST).

• Clearly distinguish:

  • Documentation comments (immediately preceding table/column).
  • Inline or interstitial comments that should not be treated as docs.

Tasks

• Add sqlparser as a dependency.
• Implement a function that:
  • Takes raw SQL text and parsed statements.
  • For each CREATE TABLE:
    • Extracts table-level doc comments from lines directly above the CREATE TABLE line.
    • Extracts column-level doc comments from lines directly above each column definition line.
• Decide and document the exact rules for:
  • When a comment block is considered “attached” to a table/column.
  • When a comment should be ignored (e.g. separated by blank lines or other code).