Feat/mlx binding

[kerthcet]

What this PR does / why we need it

Which issue(s) this PR fixes

Fixes #

Special notes for your reviewer

Does this PR introduce a user-facing change?

[Copilot]

Pull request overview

This PR significantly expands PUMA from a basic CLI into a more complete local-model runtime by adding: (1) a SQLite-backed model registry + caching utilities, (2) Hugging Face download support with progress, (3) an OpenAI-compatible HTTP API server, and (4) an (early/placeholder) MLX backend gated to macOS + mlx feature.

Changes:

• Introduces a new model registry/storage layer (SQLite) and CLI commands (pull, ls, inspect, rm, serve, info) that operate on it.
• Adds an Axum-based OpenAI-compatible API server (chat + legacy completions + models + health) with streaming support for chat.
• Adds MLX backend scaffolding (feature-gated) plus documentation/examples, along with CI/lint/test targets and refreshed docs.

Reviewed changes

Copilot reviewed 48 out of 52 changed files in this pull request and generated 15 comments.

Show a summary per file

File	Description
tests/cli_test.rs	Adds CLI integration tests that execute the built binary end-to-end.
src/utils/mod.rs	Introduces utils module root.
src/utils/format.rs	Adds formatting helpers for sizes, parameters, and relative timestamps (with unit tests).
src/utils/file.rs	Adds cache/home path helpers (including PUMA_HOME override) and file utilities.
src/util/request.rs	Removes legacy chunked downloader implementation.
src/util/mod.rs	Removes old util module root.
src/util/file.rs	Removes old home-dir helper (migrated into utils).
src/system/system_info.rs	Adds system info collection (OS/arch/mem/GPU/cache stats) and display output.
src/system/mod.rs	Introduces system module root.
src/storage/storage_trait.rs	Adds ModelStorage trait abstraction for registry backends.
src/storage/sqlite.rs	Implements SQLite-backed model storage with migrations + filtering + tests.
src/storage/mod.rs	Exposes storage modules and re-exports storage types.
src/registry/model_registry.rs	Adds the model registry facade (register/load/get/remove + cache cleanup) and tests.
src/registry/mod.rs	Introduces registry module root.
src/main.rs	Wires in new modules and switches logging to tracing_subscriber.
src/downloader/progress.rs	Adds shared multi-progress management for multi-file downloads.
src/downloader/mod.rs	Exposes downloader modules (huggingface + progress).
src/downloader/huggingface.rs	Implements Hugging Face snapshot download + metadata fetch + registry registration + tests.
src/downloader/downloader.rs	Refactors download errors and introduces Downloader trait.
src/cli/serve.rs	Adds serve command to start the HTTP API with backend selection (MLX/mock).
src/cli/rm.rs	Adds remove-model CLI logic backed by registry removal.
src/cli/mod.rs	Exposes new CLI submodules (inspect/ls/rm/serve).
src/cli/ls.rs	Adds list-models logic with regex + SQL-like filter parsing.
src/cli/inspect.rs	Adds inspect-model logic and pretty-printing of model metadata.
src/cli/commands.rs	Extends clap CLI: args structs, serve command, wired registry-backed commands.
src/backend/mod.rs	Introduces backend module root with feature-gated MLX backend.
src/backend/mock.rs	Adds mock inference engine implementation for testing/fallback.
src/backend/mlx/README.md	Documents MLX backend requirements, usage, and roadmap.
src/backend/mlx/mod.rs	Adds MLX backend module with exports.
src/backend/mlx/engine.rs	Adds placeholder MLX inference engine implementation + tests.
src/backend/engine.rs	Defines the inference engine trait + response type.
src/api/types/response.rs	Adds OpenAI-compatible response types (chat + completions + models + errors).
src/api/types/request.rs	Adds OpenAI-compatible request types (chat + completions).
src/api/types/mod.rs	Re-exports API request/response types.
src/api/tests.rs	Adds integration tests for API endpoints including streaming chat SSE.
src/api/routes.rs	Creates Axum router, shared state, tracing, and permissive CORS.
src/api/models.rs	Implements /v1/models and /v1/models/:model endpoints.
src/api/mod.rs	Adds API module root.
src/api/completions.rs	Implements legacy /v1/completions endpoint (non-streaming).
src/api/chat.rs	Implements /v1/chat/completions (stream + non-stream) handler.
site/images/logo-light.svg	Adds a light-theme logo asset.
README.md	Major documentation refresh: features, CLI/API usage, project structure, etc.
Makefile	Adds test, lint, and format targets.
hack/scripts/test_api.sh	Adds manual API testing script using curl/jq.
hack/README.md	Documents hack/ scripts usage.
examples/mlx_inference.rs	Adds an example program for MLX inference (feature gated).
docs/MLX_INTEGRATION.md	Adds detailed MLX integration guide and usage instructions.
Cargo.toml	Bumps version and adds new dependencies/features for API/registry/downloader/MLX.
.github/workflows/rust-ci.yaml	Adds GitHub Actions workflow for linting and tests.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.