Four bugs in the Nix flake, all addressed:
1. checkPhase failed with "make: python3: No such file or directory"
because `make test-c` shells out to python3 (c/Makefile: PYTHON ?=
python3) but python3 wasn't in nativeBuildInputs. Add pkgs.python3.
2. `coli serve` reported "engine is not built" even though glm was
packaged, because the engine landed in $out/bin while coli looks for
it beside itself, in libexec/colibri, or via $COLI_ENGINE (c/coli:57-
66). The wrapper now sets COLI_ENGINE to the bundled engine.
3. `coli serve` failed with ModuleNotFoundError: openai_server because
the support modules (openai_server.py, resource_plan.py, doctor.py)
were not installed. Install them and put their dir on PYTHONPATH.
4. Rebuilt the install layout into a self-contained $out/lib/colibri/
that mirrors the source tree coli expects, with $out/bin/{glm,coli}
as user-facing entry points (glm symlinked; coli wrapped).
NOTE: flake.lock is intentionally not included — it must be generated
on a Nix host via `nix flake lock` and committed separately, since it
requires narHash values that only the nix tooling can compute.
Adds a Nix flake pinned to nixos-26.05. Builds the glm engine with
gcc+OpenMP (AVX2 portable), wraps the coli Python CLI with pinned deps
(torch, safetensors, huggingface-hub, numpy), and provides a dev shell.