One-line install: make leap-finetune pip/uv installable from PyPI

PROPOSAL_one_line_install.md

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+# Proposal: One-Line Installation for leap-finetune
+
+## Problem
+
+Right now, a new user who wants to try `leap-finetune` has to do this:
+
+```bash
+curl -LsSf https://astral.sh/uv/install.sh | sh   # install uv first
+git clone <repository-url>
+cd leap-finetune
+uv sync
+```
+
+That is four commands before they can even run the tool. More importantly, **requiring a `git clone` signals that this is a work-in-progress research repo, not a production-ready tool**. Developers evaluating the tool will bounce off this friction before they ever run a training job.
+
+The goal of this proposal is to reduce the install story to a single command, regardless of whether the user prefers `pip` or `uv`:
+
+```bash
+pip install leap-finetune
+# or
+uv tool install leap-finetune
+```
+
+## Why This Matters for Adoption
+
+Tools in this space that have strong adoption (`trl`, `axolotl`, `unsloth`, `litgpt`) are all one-line installable from PyPI. Users expect this. A `git clone` workflow creates several real barriers:
+
+- **Cognitive overhead**: the user has to manage a cloned repo alongside their own project.
+- **Notebook and CI incompatibility**: `!git clone` in a Colab notebook or Docker image is awkward; `!pip install` is natural.
+- **Discoverability**: PyPI search and `pip install` are how most developers find and evaluate tools. No PyPI listing means no organic discovery.
+- **Trust signal**: a `pip install`-able package reads as maintained and stable. A clone-to-run repo reads as experimental.
+
+The cost of this change is low (a few hours of work). The potential upside in adoption is high.
+
+## What Needs to Change
+
+The package already has the right foundation: a `pyproject.toml` with `hatchling` as the build backend and a `[project.scripts]` entry point for the CLI. Three targeted changes are needed to make it work correctly when installed rather than cloned.
+
+### 1. Move `job_configs/` inside the package
+
+Currently `job_configs/` lives at the repo root. When the package is installed from PyPI, the repo root does not exist. The bundled example configs need to travel with the package.
+
+**Change:** move `job_configs/` to `src/leap_finetune/job_configs/`.
+
+### 2. Fix path resolution in `constants.py`
+
+`constants.py` currently computes `LEAP_FINETUNE_DIR` by walking three directory levels up from `__file__`. This works when the repo is cloned, but points to the wrong location when the package is installed into `site-packages`.
+
+**Change:** replace the directory-walking approach with `importlib.resources`, which is the standard library mechanism for locating bundled package data regardless of how the package was installed.
+
+Use a user-local directory for the tokenization cache (e.g., `~/.cache/leap-finetune/tokenized/`) instead of a path relative to the repo root.
+
+### 3. Fix `config_resolver.py` step 3
+
+The fallback lookup for bundled configs currently uses `LEAP_FINETUNE_DIR / "job_configs"`. This needs to be updated to use `importlib.resources` to find the configs bundled inside the installed package.
+
+## What Stays the Same
+
+- Users who clone the repo and run `uv sync` continue to work exactly as before. The lookup order in `config_resolver.py` checks local paths first, so a cloned-repo workflow is unaffected.
+- The `[tool.uv] no-build-isolation-package = ["flash-attn"]` setting handles the `flash-attn` build requirement automatically for `uv` users. `pip` users on Linux will need to run `pip install flash-attn --no-build-isolation` before installing `leap-finetune`. This is a pre-existing constraint of `flash-attn` itself, not something introduced by these changes.
+
+## Nice-to-Have (Out of Scope for This PR)
+
+A `leap-finetune init` subcommand that writes a starter config file to the current directory. This would complete the getting-started flow:
+
+```bash
+pip install leap-finetune
+leap-finetune init        # scaffolds a starter config in the current directory
+leap-finetune my_job.yaml
+```
+
+This is a separate, incremental improvement and does not need to land in the same change.
+
+## Summary
+
+| | Before | After |
+|---|---|---|
+| Install steps | 4 (install uv, clone, cd, sync) | 1 |
+| Works with pip | No | Yes |
+| Works with uv tool install | No | Yes |
+| Works in notebooks/Docker | No | Yes |
+| Discoverable on PyPI | No | Yes |
+| Code changes required | | ~3 small file changes |