refactor: clean up sendability naming and flush-gate count typing

[knoepfel]

• Code

  • Rename move_constructible_only to sendable_by_move.
  • Store flush_gate::committed_counts_ by value instead of through a shared pointer.
  • Update committed_counts() and roll_up_child() to use references.
  • Remove pointer dereferencing, null handling, and unused includes.

• Tests

  • Update flush-gate tests to construct data_cell_counts by value.
  • Preserve spill-count accumulation and child-to-parent propagation coverage.

Replaces storing a committed-counts data member as a shared pointer by storing it by value instead.
Before PR #540 was merged, the committed-counts data member needed to be sent to downstream
nodes. The type of the member was not copyable, so a shared pointer to that type was used instead.
This has been fixed with this PR.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Organization UI

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Run ID: 319f8c80-bb3b-4607-920a-16133e98a09b

📥 Commits

Reviewing files that changed from the base of the PR and between 448de24 and c392c6a.

📒 Files selected for processing (4)

• phlex/core/fold/send.hpp
• phlex/model/flush_gate.cpp
• phlex/model/flush_gate.hpp
• test/flush_gate_test.cpp

📜 Recent review details

🧰 Additional context used

📓 Path-based instructions (3)

**/*.{cpp,cc,cxx,h,hpp}

📄 CodeRabbit inference engine (.github/copilot-instructions.md)

**/*.{cpp,cc,cxx,h,hpp}: Use clang-format tool for all C++ code formatting (VS Code auto-formats on save); configuration defined in .clang-format with 100-character line limit and 2-space indentation
Follow clang-tidy recommendations defined in .clang-tidy

Files:

• phlex/model/flush_gate.hpp
• test/flush_gate_test.cpp
• phlex/core/fold/send.hpp
• phlex/model/flush_gate.cpp

**/*.{hpp,cpp}

📄 CodeRabbit inference engine (AGENTS.md)

**/*.{hpp,cpp}: Use .hpp for header files, .cpp for implementation, and *_test.cpp for test files in C++
Enforce 100-character line limit and 2-space indentation in C++ code via .clang-format
Use QualifierAlignment: Right (east-const) style: int const x not const int x in C++
Use PointerAlignment: Left in C++ (pointer * attached to type, not variable name)
All C++ identifiers must use lower_case naming: namespaces, classes, structs, enums, functions, variables, parameters, members, and constants
Exception to C++ naming: template parameters use CamelCase
Exception to C++ naming: macros use UPPER_CASE
Private, protected, and constant members in C++ must have a trailing underscore (_), no trailing underscore on anything else
Use enum class preferred over plain enum in C++
Use std::shared_ptr for shared ownership, std::unique_ptr for exclusive ownership, raw pointers for non-owning references only in C++
Use functors with agent-noun pattern: ModelEvaluator evaluate_model(...) in C++
Apply .clang-tidy checks for bugprone, cert, clang-analyzer, concurrency, cppcoreguidelines, misc, modernize, performance, portability, and readability as defined in the .clang-tidy configuration file
Use phlex:: namespace for core code, phlex::experimental:: for experimental features in C++

Files:

• phlex/model/flush_gate.hpp
• test/flush_gate_test.cpp
• phlex/core/fold/send.hpp
• phlex/model/flush_gate.cpp

**/*.hpp

📄 CodeRabbit inference engine (AGENTS.md)

Avoid boolean parameters in C++ interfaces; prefer enumerations instead

Files:

• phlex/model/flush_gate.hpp
• phlex/core/fold/send.hpp

🔇 Additional comments (5)

phlex/core/fold/send.hpp (1)

33-33: 🎯 Functional Correctness

No remaining repository references to the old concept.

phlex/model/flush_gate.hpp (2)

43-43: LGTM!

Also applies to: 70-70, 88-88

---

61-61: 🩺 Stability & Availability

No change needed.

Current committed_counts() callers consume the returned reference immediately in roll_up_child(), so there is no dangling-reference path here for this PR.

phlex/model/flush_gate.cpp (1)

3-11: LGTM!

Also applies to: 22-28, 38-41, 86-86

test/flush_gate_test.cpp (1)

29-29: LGTM!

Also applies to: 225-231

---

📝 Walkthrough

Walkthrough

The PR renames a sendability concept and updates its specialization. It also changes flush_gate committed-count storage and roll-up APIs from shared pointers to direct values and references, with corresponding test updates.

Changes

Sendability concept rename

Layer / File(s)	Summary
Rename sendability concept phlex/core/fold/send.hpp	move_constructible_only is renamed to sendable_by_move, and sendable_type_impl uses the new concept name.

Flush gate count ownership

Layer / File(s)	Summary
Use direct flush count values phlex/model/flush_gate.hpp, phlex/model/flush_gate.cpp, test/flush_gate_test.cpp	flush_gate stores committed_counts_ by value, returns it by const reference, accepts child counts by const reference, and updates tests to construct counts by value.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• Rename move_constructible_only to clarify sendability semantics #812 — The issue directly covers the move_constructible_only to sendable_by_move rename.

Possibly related PRs

• Framework-R-D/phlex#796 — This PR overlaps with the flush_gate::roll_up_child API change to data_cell_counts const&.

Suggested reviewers: aolivier23

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes both main refactoring changes: sendability naming and flush-gate count typing.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

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• Create PR with unit tests

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[pcanal]

LGTM (although the commit log commit enhance with more detail on the 'why' of the changes).