Fix execution test setup and preemption

[ktyang512]

Fixes #759.

The execution test relied on controller-manager ROS arguments being forwarded
to controller nodes. Current ros2_control no longer does that, so the Panda
trajectory controller started without its joints parameter. The controller
failed to load, the combined spawner stopped before starting the joint-state
broadcaster, and the test observed the self-colliding default state.

This passes the existing controller YAML explicitly through the spawner's
--param-file option.

Once controller setup succeeds, the preemption case reaches a second issue:
Task::execute() waits for the cancel response with the free
spin_until_future_complete(node, future) helper even though that node already
belongs to its local executor. Reusing the existing executor avoids adding the
node twice and preserves the expected PREEMPTED result.

Finally, the post-shutdown assertion now checks the actual test executable.
The previous all-process assertion also attributed an existing released
move_group teardown crash to this MTC test; the same crash is present in the
unmodified base CI run after the functional test process stops.

Validation:

• Rolling focused execution test passed, including five consecutive repeats
• Jazzy: 6 packages built; 170 tests, 0 failures, 3 skipped
• Kilted: 6 packages built; 170 tests, 0 failures, 3 skipped
• Lyrical: 6 packages built; 170 tests, 0 failures, 19 skipped
• Kilted Clang 18 build, repository clang-tidy checks with warnings as errors,
  and focused execution test passed
• Rolling ASan build and all 14 sanitizer-enabled C++ test targets passed
  (test_execution is intentionally disabled by the existing CMake condition
  when -fsanitize is present)
• pre-commit, clang-format, and git diff --check passed

Summary by CodeRabbit

• Bug Fixes
  • Improved controller startup by ensuring the configured controller parameters are loaded correctly.
  • Refined shutdown validation to check the relevant test process exit code accurately.
  • Improved action cancellation reliability during task execution.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 430cbda2-3ab3-4ce8-a92c-7c5c987c8982

📥 Commits

Reviewing files that changed from the base of the PR and between d183144 and ed02780.

📒 Files selected for processing (2)

• capabilities/test/test_execution.launch.py
• core/src/task.cpp

Included review availability: Your plan includes up to 3 reviews per rolling hour; 2 remain after this review.

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📝 Walkthrough

Walkthrough

The pull request fixes ROS 2 controller configuration passing, narrows launch-test exit-code validation to the target process, and completes preemption cancellation through the local executor.

Changes

Execution fixes

Layer / File(s)	Summary
Execution test launch and validation capabilities/test/test_execution.launch.py	The controller spawner receives ros2_controllers_path through --param-file. The exit-code test validates the selected test process.
Preemption cancellation completion core/src/task.cpp	Preemption cancellation uses the local SingleThreadedExecutor to await completion.

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

Merge Risk: ⚪ Minimal · up to ed027

The changes correct test setup and preemption handling, with the reported focused, cross-distribution, sanitizer, static-analysis, and formatting checks passing; no actionable merge-blocking risk remains beyond normal review.

🚥 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 the execution test setup and preemption fixes.
Linked Issues check	✅ Passed	The launch change addresses the controller setup identified as the cause of the colliding start state in [#759].
Out of Scope Changes check	✅ Passed	The test setup and cancellation changes directly support the stated execution test and preemption objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[rhaschke]

Thanks for handling this issue!