Moved most tpps out of hpps

[lsawade]

Description

Moving definitions out of hpp's to tpp's and instantiating some things where possible in cpp's. Incremental building is already much better.

Issue Number

Adds to #1651

Checklist

Please make sure to check developer documentation on specfem docs.

• I ran the code through pre-commit to check style
• THE DOCUMENTATION BUILDS WITHOUT WARNINGS/ERRORS
• I have added labels to the PR (see right hand side of the PR page)
• My code passes all the integration tests
• I have added sufficient unittests to test my changes
• I have added/updated documentation for the changes I am proposing
• I have updated CMakeLists to ensure my code builds
• My code builds across all platforms

[Copilot]

Pull request overview

This PR continues the compile-time improvement effort (#1651) by moving template definitions out of public headers into .tpp files and adding explicit template instantiations in .cpp files where possible, reducing recompilation blast radius and improving incremental builds.

Changes:

• Add extern template declarations in several headers and move the corresponding template definitions out of those headers.
• Add explicit template instantiation definitions for selected templates in .cpp translation units (e.g., program header printing, assembly info, locate_sources).
• Convert specfem::attenuation from a header-only INTERFACE target to a compiled (STATIC) library, and update unit tests to include needed .tpp files.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/unit-tests/attenuation/compute_tau_sigma_tests.cpp	Includes compute_tau_sigma.tpp directly after template definitions were moved out of headers.
tests/unit-tests/attenuation/compute_tau_eps_tests.cpp	Includes compute_tau_eps.tpp/compute_tau_sigma.tpp to make template definitions visible for test-only instantiations.
tests/unit-tests/attenuation/compute_factors_tests.cpp	Includes compute_factors.tpp to access template definitions in tests.
tests/unit-tests/assembly/sources/sources.cpp	Adds missing include for compute_source_array.hpp after header dependency changes.
core/specfem/program/program.cpp	Adds program.tpp include and explicit instantiations for print_header (dim2/dim3).
core/specfem/program/CMakeLists.txt	Links specfem::program against specfem::attenuation.
core/specfem/program.hpp	Adds extern template declarations for print_header and removes direct .tpp inclusion.
core/specfem/attenuation/compute_tau_sigma.hpp	Replaces .tpp inclusion with an extern template declaration.
core/specfem/attenuation/compute_tau_eps.hpp	Replaces .tpp inclusion with an extern template declaration.
core/specfem/attenuation/compute_factors.hpp	Replaces .tpp inclusion with extern template declarations.
core/specfem/attenuation/CMakeLists.txt	Switches attenuation target from INTERFACE to STATIC.
core/specfem/assembly/sources/impl/locate_sources.hpp	Replaces .tpp inclusion with extern template declarations (dim2/dim3).
core/specfem/assembly/sources/dim2/sources.cpp	Includes locate_sources.tpp and explicitly instantiates locate_sources<dim2>.
core/specfem/assembly/sources/dim3/sources.cpp	Includes locate_sources.tpp and explicitly instantiates locate_sources<dim3>.
core/specfem/assembly/info.hpp	Replaces .tpp inclusion with extern template declarations for constructors (dim2/dim3).
core/specfem/assembly/info.cpp	Includes info.tpp and explicitly instantiates Info constructors (dim2/dim3).
core/specfem/assembly/assembly/dim3/assembly.hpp	Removes an unnecessary include (compute_source_array.hpp).

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[Copilot]

specfem_attenuation is now created as a STATIC library from *.cpp sources, but this directory currently contains no .cpp files. With an empty ATTENUATION_SOURCES list, CMake typically errors out with “No SOURCES given to target …”, and even if it configures, the library would be an empty archive and cannot host the explicit template instantiations implied by the new extern template declarations. Add at least one .cpp (e.g., an instantiation/translation unit) to this directory and list it here, or keep the target as an INTERFACE library until there are compiled sources.

[Copilot]

This extern template declaration suppresses implicit instantiation of compute_tau_sigma<specfem::constants::N_SLS> in every TU including this header. I couldn’t find any corresponding explicit instantiation definition (i.e., a .cpp that includes compute_tau_sigma.tpp and has a template ... compute_tau_sigma<specfem::constants::N_SLS>(...) line), so calls such as in core/specfem/program/qplots.cpp will end up with an undefined reference at link time. Add a single explicit instantiation definition in the specfem_attenuation library (or remove the extern template until that exists).

Suggested change

	extern template Kokkos::View<type_real[specfem::constants::N_SLS],
	Kokkos::LayoutRight, Kokkos::HostSpace>
	specfem::attenuation::compute_tau_sigma<specfem::constants::N_SLS>(
	const type_real, const type_real);

[Copilot]

Same issue as compute_tau_sigma.hpp: this extern template declaration requires a matching explicit instantiation definition in exactly one compiled translation unit. A repository-wide search didn’t find any .cpp explicitly instantiating compute_tau_eps<specfem::constants::N_SLS>, so any TU calling it (e.g., qplots.cpp) will compile but fail to link. Add the explicit instantiation definition in the attenuation library (or drop the extern template here).

[Copilot]

These extern template declarations suppress implicit instantiation for the specfem::constants::N_SLS specializations, but there is no corresponding explicit instantiation definition in any .cpp (searching the repo found none). That will produce unresolved externals anywhere these functions are used without including the .tpp. Add explicit instantiation definitions for both functions in a single .cpp compiled into specfem_attenuation, or remove these extern template declarations.