feat: add CREATE PROCEDURE grammar support

[NotMyself]

Summary

• Adds create_procedure statement rule with support for PostgreSQL (dollar-quoted bodies, OR REPLACE, LANGUAGE, SECURITY), T-SQL (AS BEGIN...END with optional DECLARE), and MySQL/MariaDB (DEFINER clause, IF NOT EXISTS)
• Adds drop_procedure with IF EXISTS and CASCADE support
• Resolves the // TODO: procedure in comment.js by adding COMMENT ON PROCEDURE support

Context

Filed as #354 — the original issue reported both CREATE PROCEDURE and CREATE TRIGGER as missing, but after examining the grammar, CREATE TRIGGER is already fully implemented. The real gap was CREATE PROCEDURE only (the issue has been updated with this correction).

Implementation

Mirrors the existing create-function.js pattern:

• New file grammar/statements/create-procedure.js with create_procedure, procedure_body, and _tsql_procedure_body_statement rules
• procedure_body reuses _function_body_statement and function_declaration from the function grammar
• Key difference from functions: no RETURNS clause, and the T-SQL body variant doesn't require a RETURN statement

Test plan

• tree-sitter generate succeeds with no new warnings
• 10 new test cases in test/corpus/procedures.txt covering:
  • PostgreSQL: simple procedure, OR REPLACE, no parameters, SECURITY DEFINER
  • T-SQL: basic, with DECLARE, nested BEGIN-END
  • DROP PROCEDURE: basic, IF EXISTS, CASCADE
• Fixed test expectations to match actual parser output:
  • integer type: use (int (keyword_int)) consistent with existing function tests
  • INSERT: include (keyword_values) node, bare field references in list (no term wrapper)
  • DELETE/SELECT: from as sibling of delete/select under statement, matching delete.txt and select.txt patterns

Closes #354

🤖 Generated with Claude Code

[NotMyself]

Fixed the 4 failing corpus tests (Procedure with OR REPLACE (PostgreSQL), TSQL procedure, TSQL procedure with DECLARE, TSQL procedure with nested BEGIN-END).

The issue was that test expectations for schema-qualified procedure names (e.g. public.refresh_cache, dbo.GetUsers) were missing field labels on the object_reference node. The grammar defines object_reference with field('schema', ...) and field('name', ...) for two-part identifiers, so the parser produces schema: (identifier) and name: (identifier) — but the tests expected bare (identifier) nodes without field labels.

[matthias-Q]

LGTM. Thanks for the PR.