Add SQL and PL/pgSQL formatting library

.gitignore

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+/target

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+libpgfmt is a Rust library for formatting PostgreSQL-specific SQL and PL/pgSQL.
+
+## Build Commands
+
+```sh
+cargo build
+cargo test
+cargo test <test_name>    # run a single test
+cargo clippy              # lint
+cargo fmt --check         # check formatting
+cargo fmt                 # auto-format
+```

Cargo.toml

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+[package]
+name = "libpgfmt"
+version = "0.1.0"
+edition = "2024"
+description = "A Rust library for formatting PostgreSQL SQL and PL/pgSQL"
+license = "BSD-3-Clause"
+repository = "https://github.com/gmr/libpgfmt"
+keywords = ["postgresql", "sql", "formatter", "plpgsql"]
+categories = ["text-processing", "development-tools"]
+
+[dependencies]
+tree-sitter = "0.26"
+tree-sitter-postgres = "0.1"
+
+[dev-dependencies]
+pretty_assertions = "1"

src/error.rs

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+use std::fmt;
+
+/// Errors that can occur during formatting.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum FormatError {
+    /// The tree-sitter parser could not be initialized.
+    Parser(String),
+    /// The input SQL contains a syntax error.
+    Syntax(String),
+}
+
+impl fmt::Display for FormatError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            FormatError::Parser(msg) => write!(f, "Parser error: {msg}"),
+            FormatError::Syntax(msg) => write!(f, "Syntax error: {msg}"),
+        }
+    }
+}
+
+impl std::error::Error for FormatError {}