Update dependencies

[thfroitzheim]

Update for the tblite, DFT-D4, and multicharge dependencies. This PR updates the tblite dependency to the current main branch of tblite and is a draft until the 0.5.1 tblite release (tblite#305).

To make xtb compatible with the updated dependencies, I added a dedicated PTB solver and searched for the HOMO index (no longer in the tblite wavefunction). Additionally, I added consistent dependencies in meson and cmake.

[Copilot]

Pull request overview

This PR updates dependencies (tblite to main/HEAD, multicharge to v0.5.0, mctc-lib to v0.5.1, and dftd4 to v4.0.1) to make xtb compatible with the latest versions. The key changes include adding a dedicated PTB solver to replace removed tblite functionality and implementing HOMO index finding logic since it's no longer provided by the tblite wavefunction.

• Adds new PTB solver module to handle eigenvalue problems with custom orbital energy scaling
• Updates EEQ model initialization to use new_eeq_model API with error handling
• Implements HOMO index calculation based on electron count and fractional occupations

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 29 comments.

Show a summary per file

File	Description
src/ptb/solver.F90	New PTB solver implementation extending tblite's sygvd_solver with custom orbital energy scaling
src/ptb/twostepscf.F90	Replaces old get_density function with new PTB solver usage, updates EEQ model solve API
src/ptb/response.F90	Updates to use new PTB solver for polarizability calculations
src/ptb/calculator.F90	Updates EEQ model initialization to new API with error handling
src/ptb/ncoord.F90	Changes import from tblite_data_covrad to mctc_data
src/tblite/mapping.F90	Implements HOMO index calculation to replace removed tblite%homo field
src/tblite/calculator.F90	Adds error parameter to eeq_guess and imports new eeqbc_guess
src/dipro.F90	Implements HOMO index calculation for fragment analysis
test/unit/test_ptb.F90	Updates test to use new EEQ model API with error handling
subprojects/*.wrap	Updates dependency versions for tblite, multicharge, mctc-lib, and dftd4
cmake/modules/Find*.cmake	Adds/updates CMake modules for multicharge and dftd4, updates tblite and mctc-lib versions
src/ptb/meson.build	Adds solver.F90 to build
src/ptb/CMakeLists.txt	Adds solver.F90 to build

Comments suppressed due to low confidence (2)

subprojects/tblite.wrap:4

• The revision is set to 'head' which tracks the latest commit on the main branch. This can lead to non-reproducible builds and unexpected breaking changes. The PR description mentions this is intentional until tblite 0.5.1 is released, but consider pinning to a specific commit hash in the interim to ensure build reproducibility.

revision = head

cmake/modules/Findtblite.cmake:20

• The revision is set to 'HEAD' (uppercase) which tracks the latest commit. This creates inconsistency with the meson build file which uses 'head' (lowercase), and can lead to non-reproducible builds. Consider using a specific commit hash or version tag, and ensure consistency between build systems.

set(_rev "HEAD")

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[toxtran]

#1295 can be also fixed by this PR