feat: Replace file_ops WASM Component with Bazel-Native Operations

[avrabe]

Summary

Replace the custom file_ops WASM component with Bazel-native file operations to reduce dependencies and improve performance.

Current State

• Custom file_ops WASM component for cross-platform file operations
• Runs via wasmtime to copy/move/create files
• Adds overhead: wasmtime startup + WASI filesystem operations
• Used extensively in cpp_component, wit_library, etc.

Why file_ops Exists

• Cross-platform (Windows) compatibility
• Replaces shell scripts (cp, mv, mkdir)
• Provides consistent behavior

Proposed Solution

Replace file_ops with Bazel-native operations:

file_ops Operation	Bazel Alternative
copy_file	ctx.actions.symlink() or ctx.actions.run() with platform tool
create_directory	Implicit in output paths
move_file	ctx.actions.run() with platform tool
concatenate_files	ctx.actions.write() or small helper binary

For Complex Cases

Use a small Go binary (already have Go toolchain for wac_deps tool).

Benefits

• Remove wasmtime dependency from basic builds
• Faster file operations (no WASM overhead)
• Simpler debugging (native tools)
• Smaller toolchain footprint

Risks

• file_ops was created to solve real cross-platform issues
• Need to verify Bazel-native alternatives work on Windows
• Some operations may not have direct equivalents

New Features Enabled

• Pure Bazel builds without runtime dependencies
• Better integration with Bazel's action cache

Impact

• Effort: Medium
• Risk: Medium
• Value: Medium

Related

• Phase 4 shell elimination work already reduced file_ops usage

[avrabe]

Closing - the file_ops WASM component is intentionally our own implementation and demonstrates the capabilities of the WebAssembly component model. This aligns with the project's goal of showcasing WASM components for real-world tooling.