Add foundational BAML language compiler infrastructure (#2684)

Set up the core compiler pipeline with lexer, parser, HIR, THIR, and
codegen stages, organized as a Rust workspace with modular crates for
each compilation phase. Includes comprehensive test infrastructure with
snapshot testing and benchmarks for compiler performance.

RUN_CODSPEED=1


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduces a modular Rust workspace for the BAML compiler
(lexer→parser→HIR→THIR→codegen) with diagnostics, auto-generated
snapshot tests and CodSpeed benchmarks, and comprehensive CI plus dev
hooks.
> 
> - **BAML Language Workspace**:
> - Add Rust workspace `baml_language` with crates: `baml_base`,
`baml_lexer`, `baml_parser`, `baml_syntax`, `baml_hir`, `baml_thir`,
`baml_codegen`, `baml_workspace`, `baml_diagnostics`, `baml_db`.
> - Implement lossless lexer (Logos), stub parser (Rowan), syntax
kinds/nodes, HIR/THIR data structures and helpers, diagnostics rendering
(Ariadne), and bytecode model stubs.
> - **Tests & Benchmarks**:
> - New `baml_tests` crate with build script to auto-generate snapshot
tests from `projects/` and instrumented benchmarks from `benches/`
(incremental and scale scenarios).
> - Add snapshots, benchmark datasets, and bench harness
(CodSpeed-compatible).
> - **CI/CD**:
> - Add `.github/workflows/ci.yaml` running fmt, clippy, tests
(Linux/macOS/Windows), WASM build, MSRV check, cargo-deny, snapshot
tests, and CodSpeed benchmarks (opt-in via flags/paths).
> - **Dev Tooling**:
> - Add git pre-commit hook setup (`scripts/setup-hooks.sh`) and docs;
workspace `rustfmt.toml`, `rust-toolchain.toml`, `deny.toml`; update
`.gitignore`.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
3491f84. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Claude <[email protected]>

Author: hellovai

.github/workflows/ci.yaml

@@ -116,7 +116,6 @@ $RECYCLE.BIN/
 /out/
 engine/language_client_ruby/**/*.bundle
 engine/target/
-Cargo.lock
 Icon
 Network Trash Folder
 Temporary Items
@@ -175,3 +174,4 @@ trace_events_debug.json
 
 result
 
+target/

.gitignore

@@ -0,0 +1,4 @@
+# Additional target directories that don't invalidate the main compile cache when changing linker settings,
+# e.g. `CARGO_TARGET_DIR=target-maturin maturin build --release --strip` or
+# `CARGO_TARGET_DIR=target-llvm-lines RUSTFLAGS="-Csymbol-mangling-version=v0" cargo llvm-lines -p ruff --lib`
+/target*