feat(cross-cutting): added pi-ast/pi-shell crates and rewired pi-natives

- Added `pi-ast` as a new crate with public `language`, `ops`, and `summary` modules and exported `SupportLang`.
- Added AST summary and rewrite APIs in `pi-ast`, including language inference, overlap-safe edits, and span normalization.
- Added `pi-shell` crate with new `Shell` and cross-platform `Process` APIs, session execution, and cancellation-aware runs.
- Updated `pi-natives` to use shared `pi_ast`/`pi_shell` APIs, switched to local path deps, and moved minimizer assets to `pi-shell`.

crates/pi-shell/build.rs

@@ -0,0 +1,62 @@
+use std::{
+	env,
+	fmt::Write as _,
+	fs,
+	path::{Path, PathBuf},
+};
+
+fn main() {
+	generate_minimizer_builtin_filters();
+}
+
+fn generate_minimizer_builtin_filters() {
+	let manifest_dir = env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR should be set");
+	let defs_dir = Path::new(&manifest_dir)
+		.join("src")
+		.join("minimizer")
+		.join("defs");
+	let out_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR should be set"));
+	let output_path = out_dir.join("builtin_filters.toml");
+
+	println!("cargo:rerun-if-changed={}", defs_dir.display());
+
+	let mut concatenated =
+		String::from("# Auto-generated by build.rs -- do not edit.\nschema_version = 1\n\n");
+
+	let mut entries: Vec<PathBuf> = Vec::new();
+	if let Ok(read_dir) = fs::read_dir(&defs_dir) {
+		for entry in read_dir.flatten() {
+			let path = entry.path();
+			if path.extension().and_then(|extension| extension.to_str()) == Some("toml") {
+				entries.push(path);
+			}
+		}
+	}
+	entries.sort();
+
+	for path in entries {
+		println!("cargo:rerun-if-changed={}", path.display());
+		match fs::read_to_string(&path) {
+			Ok(body) => {
+				let filename = path
+					.file_name()
+					.and_then(|name| name.to_str())
+					.unwrap_or("unknown");
+				writeln!(concatenated, "# --- {filename} ---").expect("write to String");
+				for line in body.lines() {
+					let trimmed = line.trim_start();
+					if trimmed.starts_with("schema_version") {
+						continue;
+					}
+					concatenated.push_str(line);
+					concatenated.push('\n');
+				}
+				concatenated.push('\n');
+			},
+			Err(error) => panic!("failed to read filter definition {}: {error}", path.display()),
+		}
+	}
+
+	fs::write(&output_path, concatenated)
+		.unwrap_or_else(|error| panic!("failed to write {}: {error}", output_path.display()));
+}