Add parameter macro detection (#86)

[rathboma]

Summary

Implements parameter macro parsing as requested in issue #86.

• Detects -- %name% = value (inline) and /* %name% = value */ (block) comment declarations before a SQL statement
• Exposes them as parameterMacros: Record<string, string> on both Statement and IdentifyResult
• Macros are scoped to the immediately following statement — they do not bleed across statement boundaries
• Macro value is everything after =, trimmed of whitespace

Example:

-- %id% = 7
SELECT * FROM table WHERE id = %id%;

Returns parameterMacros: { id: '7' } on the SELECT result. Substitution of %id% in the SQL body is left to consumers (e.g. Beekeeper Studio).

Test plan

• Single inline macro before a statement
• Multiple inline macros before a statement
• Block comment macro syntax
• Macros do not bleed into subsequent statements
• Empty parameterMacros: {} when no macros declared
• All 489 existing tests continue to pass

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