feat: Integrate standalone FidelityComputer (WIP - some tests failing)

[Akhils777]

Description

This PR integrates the new FidelityComputer system, replacing the previous dependency on qutip_qtrl.fid_computer.

Note: This is a work-in-progress merge. 3 test cases are currently failing (listed below), and fixes are actively being developed.

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Key Improvements

• Introduced fidcomp.py with support for:
  • PSU / SU / TRACEDIFF fidelity types
  • State and process fidelity
  • JAX compatibility
• Refactored optimization algorithms to use the new fidelity system

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Known Failing Test Cases:

1. State-to-state GRAPE optimization
2. State-to-state CRAB optimization
3. Parameterized CRAB optimization

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Verification

• All other test cases pass with numerical consistency
• Improved fidelity handling and input type compatibility
• Side-by-side equivalence with legacy fidelity module

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[coveralls]

Pull Request Test Coverage Report for Build 14846815312

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 185 of 345 (53.62%) changed or added relevant lines in 8 files are covered.
• 59 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-15.8%) to 70.815%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/qutip_qoc/_jopt.py	13	16	81.25%
src/qutip_qoc/_optimizer.py	18	22	81.82%
src/qutip_qoc/fidcomp.py	58	65	89.23%
src/qutip_qoc/_rl.py	45	73	61.64%
src/qutip_qoc/_grape.py	6	39	15.38%
src/qutip_qoc/pulse_optim.py	22	60	36.67%
src/qutip_qoc/_crab.py	7	54	12.96%

Files with Coverage Reduction	New Missed Lines	%
src/qutip_qoc/_jopt.py	1	90.77%
src/qutip_qoc/_optimizer.py	2	83.45%
src/qutip_qoc/objective.py	4	90.48%
src/qutip_qoc/result.py	13	73.2%
src/qutip_qoc/_grape.py	14	16.0%
src/qutip_qoc/pulse_optim.py	25	36.36%

Totals
Change from base Build 14120830666:	-15.8%
Covered Lines:	791
Relevant Lines:	1117

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💛 - Coveralls