feat: Add environment information CLI

[matthewfeickert]

Description

Resolves #1580

Add pyhf.utils.environment_info which produces a Markdown-friendly bullet list summary of the environment useful for bug reports. Also adds a CLI command pyhf utils environment. Optional backends (iminuit, jax, jaxlib) show "not installed" when absent.

Example output:

$ pyhf utils environment
* os version: macOS 14.6.1
* kernel version: Darwin 23.6.0 arm64
* python version: CPython 3.12.7 [Clang 16.0.0 (clang-1600.0.26.4)]
* pyhf version: 0.8.0.dev0
* numpy version: 2.1.3
* scipy version: 1.14.1
* iminuit version: 2.30.1
* jax version: not installed
* jaxlib version: not installed

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

---

* Add pyhf.utils.environment_info() to produce OS, Python, pyhf, numpy,
  scipy, and optional backend (iminuit, jax, jaxlib) version information
  as a Markdown-friendly bullet list for bug reports. Optional packages
  show "not installed" when absent.
* Add pyhf utils environment CLI command with --output-file option.
* Add tests for environment_info() including missing optional packages
  via monkeypatch, and CLI tests via script_runner.

Co-authored-by: Giordon Stark <kratsg@gmail.com>

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.30%. Comparing base (24b1013) to head (ff8ba4c).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2129      +/-   ##
==========================================
+ Coverage   98.28%   98.30%   +0.02%     
==========================================
  Files          65       66       +1     
  Lines        4305     4360      +55     
  Branches      465      470       +5     
==========================================
+ Hits         4231     4286      +55     
  Misses         46       46              
  Partials       28       28              

Flag	Coverage Δ
contrib	98.05% <89.65%> (-0.12%)	⬇️
doctest	98.16% <89.65%> (-0.12%)	⬇️
unittests-3.10	96.37% <89.65%> (-0.10%)	⬇️
unittests-3.11	96.37% <89.65%> (-0.10%)	⬇️
unittests-3.12	96.37% <89.65%> (-0.10%)	⬇️
unittests-3.13	96.37% <89.65%> (-0.10%)	⬇️
unittests-3.9	96.58% <100.00%> (+0.04%)	⬆️

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