Add ps_calib vctr

[malcolmbarrett]

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[Copilot]

Pull Request Overview

This PR introduces a new ps_calib vector class to replace the use of psw objects for calibrated propensity scores, providing a more specialized type for propensity score calibration functionality.

• Creates a new ps_calib vector class with comprehensive vctrs machinery
• Updates ps_calibrate() to return ps_calib objects instead of psw objects
• Adds weight calculation methods for the new ps_calib class

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
R/ps_calibration.R	Implements new ps_calib class with constructor, vctrs methods, and updates ps_calibrate() function
R/weights.R	Adds weight calculation methods (wt_ate, wt_att, etc.) for ps_calib objects
R/weights-utils.R	Updates utility function to handle ps_calib objects in weight calculations
man/ps_calibrate.Rd	Updates documentation to reflect return of ps_calib instead of psw objects
tests/testthat/test-ps_calibration.R	Updates tests to expect ps_calib class and adds new metadata testing
NAMESPACE	Exports new S3 methods for the ps_calib class

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