Fix Spectral combination

[obackhouse]

• Fixes Spectral.combine, which is now separated into Spectral.combine_for_self_energy and Spectral.combine_for_greens_function. The choice of functions depends on which quantity you want to exactly conserve when combining the Spectral objects, which may not allow conservation of both in many cases.
• Fixes some non-Dyson classification, which I had confused myself about.
• Removes GW expression. This is not rigorously wavefunction-based and breaks the Spectral logic. It should live in momentGW and combination handled there (as it already is).
• Some typing improvements.

[Copilot]

@obackhouse I've opened a new pull request, #19, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

Pull request overview

This PR fixes the Spectral.combine method to properly concatenate Dyson orbitals and handle the linear algebra for constructing full eigenvectors. It also removes the GW/TDAGW expression (which should live in momentGW instead), fixes non-Dyson classification for ADC expressions, and adds typing improvements.

Key changes:

• Reimplements Spectral.combine to concatenate Dyson orbitals and use project_eigenvectors for proper eigenspace construction
• Removes the TDAGW/GW expression from the codebase as it breaks Spectral logic
• Fixes ADC non_dyson property from False to True and removes HF_Dyson class
• Moves project_eigenvectors from exact.py to util/linalg.py with improved signature allowing eigvecs=None
• Adds typing-extensions dependency and uses Self type for better type hints

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
dyson/representations/spectral.py	Reimplements combine() method to concatenate Dyson orbitals and construct eigenvectors; fixes typo in error message
dyson/util/linalg.py	Adds project_eigenvectors() function (moved from exact.py) with support for eigvecs=None parameter
dyson/util/init.py	Exports new project_eigenvectors function
dyson/solvers/static/exact.py	Removes project_eigenvectors() (moved to util/linalg.py) and updates import
dyson/solvers/static/davidson.py	Updates import to use project_eigenvectors from util
dyson/solvers/static/mblse.py	Updates return type annotations from MBLSE to MLSE for MLSE class methods
dyson/solvers/solver.py	Adds Self type import and uses it for return type annotations
dyson/expressions/expression.py	Removes "dyson"/"central" expression support from ExpressionCollection, adds Self type usage
dyson/expressions/hf.py	Removes HF_Dyson class as it's no longer needed
dyson/expressions/adc.py	Changes non_dyson property from False to True
dyson/expressions/gw.py	File completely removed (TDAGW expression)
dyson/expressions/init.py	Removes TDAGW import
dyson/init.py	Removes TDAGW from public API and documentation
tests/test_expressions.py	Removes TDAGW tests, adds comprehensive combine() tests for HF/CCSD/FCI/ADC2/ADC2x with both Exact and Davidson solvers, adds incomplete comment
tests/test_mblse.py	Removes skip conditions for "Dyson only" expressions
tests/test_mblgf.py	Removes skip conditions for "Dyson only" expressions
tests/test_exact.py	Removes skip conditions for "Dyson only" expressions
tests/test_downfolded.py	Removes skip conditions for "Dyson only" expressions
tests/test_density.py	Removes skip conditions for "Dyson only" expressions
tests/test_davidson.py	Removes skip conditions for "central Hamiltonian" and "Dyson only" expressions
tests/test_cpgf.py	Removes skip conditions for "central Hamiltonian"
tests/test_corrvec.py	Removes skip conditions for "central Hamiltonian"
tests/conftest.py	Removes TDAGW from METHODS list and simplifies _get_central_result() by removing dyson-specific logic
pyproject.toml	Adds typing-extensions>=4.0.0 to dev dependencies

Comments suppressed due to low confidence (1)

dyson/representations/spectral.py:288

• This assignment to 'eigvecs' is unnecessary as it is redefined before this value is used.

        eigvecs = util.project_eigenvectors(

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[obackhouse]

ok this has broken stuff for higher order moments after recombinations 😢

[codecov]

Codecov Report

❌ Patch coverage is 79.24528% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.89%. Comparing base (76caa9a) to head (6a717da).
⚠️ Report is 20 commits behind head on master.

Files with missing lines	Patch %	Lines
dyson/representations/spectral.py	80.32%	5 Missing and 7 partials ⚠️
dyson/representations/lehmann.py	0.00%	5 Missing ⚠️
dyson/util/linalg.py	92.00%	1 Missing and 1 partial ⚠️
dyson/expressions/adc.py	0.00%	1 Missing ⚠️
dyson/expressions/expression.py	80.00%	1 Missing ⚠️
dyson/solvers/solver.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #18      +/-   ##
==========================================
- Coverage   72.37%   71.89%   -0.48%     
==========================================
  Files          38       37       -1     
  Lines        3873     3790      -83     
  Branches      494      493       -1     
==========================================
- Hits         2803     2725      -78     
+ Misses        869      859      -10     
- Partials      201      206       +5     

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[Copilot]

Pull request overview

Copilot reviewed 30 out of 30 changed files in this pull request and generated 4 comments.

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