Refactor: Break up parse_statement.cpp (554 lines)

[clank-hayen]

Problem

parser/parse_statement.cpp is the largest file in the parser at 554 lines. While the parser already has good file separation (e.g., parse_if.cpp, parse_while.cpp, parse_for.cpp), parse_statement.cpp still contains significant inline logic that could be extracted:

1. Generic type declarations (lines 150-232): Parsing of List<T>, Pair<T>, Tuple<T>, Channel<T> variable declarations
2. Qualified function calls (lines 294-360): Complex logic for module.func() calls
3. Method call statements (lines 370-450): obj.method() with error handling
4. Field assignment (lines 450-500): obj.field = value parsing

Suggested Solution

Extract into smaller, focused files:

parser/
  parse_generic_type.cpp    # List<T>, Pair<T>, Tuple<T>, Channel<T> declarations
  parse_qualified.cpp       # module.func() and module.Type handling
  parse_member_access.cpp   # obj.method() and obj.field = value
  parse_statement.cpp       # Main dispatch (now much smaller)

This follows the existing pattern where parse_if.cpp, parse_for.cpp, etc. each handle their specific statement type.

Impact

• Each file becomes more focused and easier to understand
• Follows existing codebase patterns
• Easier to test individual parsing components
• Better separation of concerns