CI overhaul

[JordiManyer]

• Removed TestApp and sysimage compilation completely.
• Split tests into different runners.
• Now supporting newest stable julia release.

[Copilot]

Pull request overview

This PR overhauls the CI pipeline by removing the TestApp module and sysimage compilation, splitting tests into categorized runners controlled by a TESTCASE environment variable, and updating Julia version pins to use 'lts' and '1' (latest stable).

Changes:

• Removed TestApp module, its Project.toml, sysimage compilation scripts, and all TestApp. prefixed references in MPI tests.
• Split sequential and MPI tests into named categories (geometry, fespaces, physics, transient/adaptivity, misc) selectable via TESTCASE env var, with a CI matrix that runs each as a separate job.
• Updated CI to use julia-actions/julia-runtest@v1, added concurrency control, and modernized Julia version specifiers.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
.github/workflows/ci.yml	Consolidated into single matrix job with TESTCASE, removed sysimage steps, updated Julia versions
test/runtests.jl	Routes to sequential or MPI tests based on TESTCASE
test/sequential/runtests.jl	Groups sequential tests into categories gated by TESTCASE
test/mpi/runtests.jl	Removed sysimage support, added OpenMPI --oversubscribe flag
test/mpi/runtests_np4.jl	Replaced TestApp with direct includes of test modules
test/mpi/runtests_np4_body.jl	Replaced TestApp. prefixes, added TESTCASE gating for MPI test categories
test/TestApp/* (5 files)	Deleted TestApp module, compilation scripts, and related config

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.11%. Comparing base (f779087) to head (06c59a5).
⚠️ Report is 6 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #197       +/-   ##
===========================================
+ Coverage    0.00%   85.11%   +85.11%     
===========================================
  Files          15       16        +1     
  Lines        4228     4254       +26     
===========================================
+ Hits            0     3621     +3621     
+ Misses       4228      633     -3595     

Flag	Coverage Δ
mpi-adaptivity	45.45% <ø> (?)
mpi-fespaces	39.99% <ø> (?)
mpi-geometry	23.26% <ø> (?)
mpi-misc	50.18% <ø> (?)
mpi-physics	35.56% <ø> (?)
mpi-transient	24.78% <ø> (?)
seq-adaptivity	39.38% <ø> (?)
seq-fespaces	40.41% <ø> (?)
seq-geometry	23.30% <ø> (?)
seq-misc	34.91% <ø> (?)
seq-physics	36.63% <ø> (?)
seq-transient	24.82% <ø> (?)
sequential	?

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