[thomasple]

Summary

Closes #20. Removes the Pydantic integration. Users validate the output of convert_mapping with Pydantic or another library instead.

 src/hartreez/
 ├── __init__.py        # drops the UnitDimension export
 ├── mapping.py         # drops require_references and recurse (only pydantic.py used them)
-├── metadata.py        # UnitDimension
-└── pydantic.py        # UnitAwareModel
 tests/
-└── test_pydantic.py
 docs/
 ├── mappings.md        # + "Validate with Pydantic or another library"
-└── pydantic.md
 pyproject.toml         # drops the pydantic extra and dev dependency
 release.yml            # wheel smoke test no longer installs [pydantic]
 README.md              # Pydantic section now links to the recipe
+CHANGELOG.md           # new; linked from PyPI, renamed per release (docs/releasing.md)
 AGENTS.md              # + every user-visible PR adds a changelog entry

The recipe:

data = convert_mapping(raw, au, reference_units={"timestep": "fs", "energy": "eV"})
inputs = CalculationInput.model_validate(data)

The docs say that only paths listed in reference_units are checked, and that extra="forbid" makes Pydantic reject unknown suffixed keys such as junk[ps].

Evidence

• Before (main): from hartreez.pydantic import UnitAwareModel and from hartreez import UnitDimension import. pytest: 242 passed, 1 skipped.
  After: both raise ImportError. pytest: 197 passed, 1 skipped (torch is not installed; the 45 dropped tests are in tests/test_pydantic.py). Pyright reports no errors.
• The recipe, run with Pydantic installed, gives timestep=20.67 energy=0.0735 in au. With extra="forbid", {"energy[eV]": 1.0, "junk[ps]": 1.0} is rejected at ('junk',).
• convert_mapping behaves the same: it always passed recurse=True and never set require_references.

Merge Danger

Door: two-way

Reverting restores the integration. Once a release ships without it, users will have moved to the recipe.

Blast Radius: Pydantic users

hartreez[pydantic], hartreez.pydantic.UnitAwareModel and hartreez.UnitDimension shipped in v0.1.0 and v0.1.1. Code that uses them breaks on upgrade. The removal is recorded under ## Unreleased in the new CHANGELOG.md, so the next release should be 0.2.0.