feat: refactor devshell as modular standalone path lol

devshells/README.md

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+# Development Shells
+
+This directory contains modular Nix devShell configurations for various programming languages and use cases.
+
+## Available Shells
+
+### `default`
+Basic shell with git and nixfmt for dotfiles development.
+
+```bash
+nix develop
+```
+
+### `python-uv`
+Python development with UV package manager.
+
+```bash
+nix develop .#python-uv
+```
+
+**Includes:**
+- Python 3.12
+- UV (fast Python package manager)
+- Ruff (linter/formatter)
+- Pyright (type checker)
+
+### `ml-ai`
+Machine Learning and AI development with HuggingFace model management.
+
+```bash
+nix develop .#ml-ai
+```
+
+**Includes:**
+- Python 3.12 with huggingface-hub
+- `huggingface-cli` for downloading models
+- UV for package management
+- Git LFS for large files
+- Ruff and Pyright
+
+**Model cache:** `~/.cache/huggingface` (persistent across projects)
+
+**Example usage:**
+```bash
+# Download a TTS model
+huggingface-cli download facebook/mms-tts-eng
+
+# Download a small LLM
+huggingface-cli download meta-llama/Llama-3.2-1B
+
+# Download specific files only
+huggingface-cli download openai/whisper-large-v3 --include "*.json" "*.safetensors"
+
+# Use in your project
+uv init my-ml-project
+cd my-ml-project
+uv add transformers torch
+```
+
+### `go`
+Go development environment.
+
+```bash
+nix develop .#go
+```
+
+**Includes:**
+- Go compiler
+- gopls (language server)
+- golangci-lint
+- delve (debugger)
+
+### `web-bun`
+Modern web development with Bun runtime.
+
+```bash
+nix develop .#web-bun
+```
+
+**Includes:**
+- Bun
+- Node.js 20
+- Yarn
+- esbuild
+- vscode-langservers-extracted
+
+### `rust`
+Rust development environment.
+
+```bash
+nix develop .#rust
+```
+
+**Includes:**
+- Cargo & rustc
+- rust-analyzer
+- rustfmt
+- clippy
+
+### `zig-nightly` (optional)
+Zig nightly development (only available if zig overlay is working).
+
+```bash
+nix develop .#zig-nightly
+```
+
+## Usage from Any Directory
+
+You can use these shells from anywhere by referencing your dotfiles:
+
+```bash
+# From any directory
+cd ~/my-project
+nix develop ~/Development/dotfiles#ml-ai
+```
+
+## Auto-loading with direnv
+
+To automatically load a shell when entering a directory:
+
+```bash
+cd ~/my-ml-project
+echo "use flake ~/Development/dotfiles#ml-ai" > .envrc
+direnv allow
+```
+
+Now the shell automatically activates when you `cd` into that directory!
+
+## Adding New Shells
+
+1. Create a new file in `devshells/` (e.g., `devshells/java.nix`)
+2. Follow the pattern:
+```nix
+{ pkgs, ... }:
+
+pkgs.mkShell {
+  name = "java";
+  packages = with pkgs; [ jdk maven ];
+  shellHook = ''
+    echo "Java development shell ready"
+  '';
+}
+```
+3. Add it to `flake.nix` imports:
+```nix
+java = importShell "java";
+```
+4. Test: `nix flake check`