0.23.0

Added

• Frame: one structure inside a larger calculation (an optimizer step, an IRC point, a path image) with what was computed there. It is a ProgramOutput without input_data, since the parent's input already holds the program, model, and keywords: structure, results (a SinglePointData, never None), success, logs, traceback, execution. Frame.from_output(child_output) records a child calculation; ProgramInput.from_spec(parent_spec, frame.structure) rebuilds a step's input.
• OutputBase: success, logs, traceback, execution, the failure rule (a traceback is required), and plogs/ptraceback, shared by ProgramOutput and Frame. Outputs serialize success first and logs and execution last.
• CalcType.irc with PathData: frames in order along a path (for an IRC, reverse end, transition state, forward end) and ts_index, with transition_state, forward_barrier, and reverse_barrier.
• CalcType.path_optimization with PathOptimizationData: the path at every iteration (paths: list[PathData]) and final_path. Its input carries the chain in ProgramInput.structures["initial_chain"], endpoints included and in order.
• A shared reading interface for results holding structures: structures, energies, to_xyz(), save("*.xyz") on OptimizationData, PathData, PathOptimizationData, and ConformerSearchData.
• ProgramInput.require_structure() (returns the Structure or raises for a chain input; narrows the type for type checkers) and ProgramInput.initial_chain.

Changed

• Breaking: OptimizationData.trajectory is now OptimizationData.frames and holds Frames instead of ProgramOutputs. Read a step's structure as step.structure instead of step.input_data.structure. trajectory= and saved files with "trajectory" still load (with a FutureWarning), ProgramOutputs passed as steps become frames, and .trajectory remains as a deprecated property.
• Breaking: ScanData.trajectory is now ScanData.points, with the same compatibility.
• Breaking: ConformerSearchData.conformers and .rotamers hold Frames (each conformer's energy in frame.results.energy), sorted by energy with energy-less frames last. conformer_energies, rotamer_energies, and their *_relative forms are now properties. Lists of structures with energy arrays, and saved files in that form, still load. Read structures with .structures (conformers) or [f.structure for f in data.rotamers].
• Fields holding several results are named after what they hold: frames, paths, points, conformers, rotamers.
• Breaking: ProgramInput.structure is Structure | None. Validation requires it for every calculation type except path_optimization, which requires structures["initial_chain"] (at least two structures with the same atoms) and no structure. Type checkers no longer know structure is set; use require_structure().
• ProgramInput.structures values may be a Structure or an ordered list[Structure].