fix: ModifierResolverPass preserve non-local edges with classical DAG

[nicolaassolini-qntm]

closes #1789

When a DFG classical block is found, the DFG is copied as it is. When the DFG contained a non-local edge (a function call), an invalid hugr was generated since the edge was not copied.

[codecov]

Codecov Report

❌ Patch coverage is 94.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.77%. Comparing base (f494f3a) to head (9e8c854).

Files with missing lines	Patch %	Lines
tket/src/modifier/modifier_resolver/dfg_modify.rs	94.11%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1792      +/-   ##
==========================================
+ Coverage   85.74%   85.77%   +0.02%     
==========================================
  Files         198      198              
  Lines       31478    31527      +49     
  Branches    30033    30082      +49     
==========================================
+ Hits        26991    27041      +50     
  Misses       3208     3208              
+ Partials     1279     1278       -1     

Flag	Coverage Δ
python	91.91% <ø> (ø)
qis-compiler	74.17% <ø> (ø)
rust	85.47% <94.11%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[codspeed-hq]

Merging this PR will not alter performance

✅ 9 untouched benchmarks

---

_{Comparing na/1789-DAG-bug (9e8c854) with main (f494f3a)}

[Copilot]

Pull request overview

Fixes an invalid HUGR generation case in ModifierResolverPass by ensuring that when a classical DFG (or other sub-container) is copied wholesale, any non-local static function-call edges into that copied subtree are preserved via the resolver’s call-map reconnection mechanism.

Changes:

• Enhance copy_sub_container_no_modification to detect and preserve non-local EdgeKind::Function inputs by recording them into call_map when copying a subtree.
• Add a new Rust regression test case intended to cover external function-call edges within a DFG context under modifiers.
• Extend the classical_function.py modifier example to include a higher-order classical call inside a modified context (dagger + control).

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tket/src/modifier/modifier_resolver/dfg_modify.rs	Preserves non-local static function-call edges when copying an unmodified subtree; adds a regression test case.
test_files/modifier_examples/classical_function.py	Adds a higher-order classical call inside a modified context to exercise the reported scenario.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.