feat: add Oracle PL/SQL support (.pkb/.pks/.pls/.plb)

[ezadEzanee]

Summary

Adds Oracle PL/SQL language support to graphify's detection, registration, and extraction pipeline, enabling graphify to parse and extract knowledge from PL/SQL source files (.pkb, .pks, .pls, .plb).

Changes

1. graphify/detect.py — File classification

Added .pkb, .pks, .pls, .plb to CODE_EXTENSIONS so PL/SQL files are classified as code and processed by the extractor pipeline.

2. graphify/extract.py — Extension routing

• Route all four PL/SQL extensions to extract_sql in the _DISPATCH table
• Register them in _EXTRA_FOR_EXTENSION as requiring the [sql] optional dependency

3. graphify/extractors/sql.py — PL/SQL-aware SQL extractor

The SQL extractor now supports both tree-sitter-sql (standard SQL) and tree-sitter-plsql (Oracle PL/SQL), with graceful fallback:

• Grammar detection: tries tree_sitter_plsql first, falls back to tree_sitter_sql
• PL/SQL object extraction: creates package, package body, function, procedure, cursor, and type definition nodes
• SQL statement analysis: extracts table references from sql_statement_select, sql_statement_insert, sql_statement_update, sql_statement_delete, and sql_statement_merge
• CREATE TABLE support: handles PL/SQL grammar's table_element > table_column_definition / table_constraint structure, including FOREIGN KEY REFERENCES
• Regex fallback: recovers packages, procedures, functions, cursors, and types from SQL*Plus extracts that lack CREATE OR REPLACE headers
• FROM/JOIN/INTO references: extracts read edges from table references within PL/SQL blocks

Example

With tree-sitter-plsql installed, graphify will now extract packages, procedures, functions, table operations, and cross-references from files like:

CREATE OR REPLACE PACKAGE BODY emp_mgmt AS
  PROCEDURE hire_employee(p_emp_id NUMBER) IS
  BEGIN
    INSERT INTO employees VALUES (p_emp_id, ...);
  END;
END emp_mgmt;

Dependencies

The [sql] optional dependency in pyproject.toml will need tree-sitter-plsql added once published to PyPI.