Add conda packaging recipe and scheduled Anaconda.org upload workflow

[Copilot]

MADNESS has no conda packaging infrastructure. This adds a conda recipe and a GitHub Actions workflow to build and upload the package to Anaconda.org on a regular cadence.

New files

• conda-recipe/meta.yaml — Conda recipe declaring build deps (cmake ≥3.12, ninja, C/C++/Fortran compilers), host/run deps (openmpi, libblas, liblapack), post-install smoke tests, and full package metadata (GPL-2.0-or-later, URLs, maintainers). Version is injected via GIT_DESCRIBE_TAG env var.

• conda-recipe/build.sh — Invoked by conda-build; runs cmake+ninja in Release mode, static libs, tests off, Pthreads backend, installs into $PREFIX.

• .github/workflows/conda.yml — Workflow triggers:

  • Weekly on Sunday midnight UTC (schedule)
  • Push to master or v* tags
  • Manual workflow_dispatch

  Version is resolved from the latest git tag, falling back to parsing MADNESS_{MAJOR,MINOR,MICRO}_VERSION out of CMakeLists.txt — no hardcoded fallback. Upload to Anaconda.org (via ANACONDA_TOKEN secret) runs only on schedule, tag, or manual dispatch; PR builds build-only. Built packages are also archived as workflow artifacts. Workflow uses permissions: contents: read.

Setup required: add an ANACONDA_TOKEN repository secret (Settings → Secrets → Actions) to enable uploads.

Original prompt

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This section details on the original issue you should resolve

<issue_title>conda</issue_title>
<issue_description>regularly update madness to conda</issue_description>

<agent_instructions>once built the madness code should be uploaded to conda regularly</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes conda #679

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