packaging: add a conda-forge feedstock #140

Context

README tells conda users they don't strictly need conda ("agentsweep is pure Python with three small dependencies") — true for the happy path — but some teams already standardize their whole toolchain on conda/mamba environments and would rather conda install agentsweep than add a separate uv/pipx install just for this one tool. A conda-forge feedstock is the standard way to support that without changing the recommended install story.

What to do

• Submit a recipe to conda-forge/staged-recipes for agentsweep.
• Wire the resulting feedstock's version-bump step into the release checklist in docs/RELEASING.md.
• Add a conda install line to README, clearly marked as an alternative rather than a replacement for the uv/pipx recommendation.