Filter effective parameter changes and fix actuator controls topic instance handling

[mengchaoheng]

This PR improves the robustness of Flight Review plotting in two aspects:

1. Parameter change visualization:

   • Filters out parameter change records where the value did not actually change
     (e.g. repeated param set with identical values).
   • Effective changes are now detected by comparing against the previous value
     (initial value or last update), avoiding misleading annotations such as
     identical CAL_* parameters being shown as changes.

2. Actuator controls plotting:

   • Fixes incorrect handling of topic_instance for actuator controls.
   • The plot layer now consistently uses ActuatorControls.topic_instance
     instead of hard-coded instance values.
   • This makes actuator control plots work correctly for both
     dynamic control allocation (vehicle_torque/thrust_setpoint) and
     legacy actuator_controls_* topics.

These changes improve correctness and compatibility without altering
existing plot behavior for valid data.

Before/after plots are attached for comparison.

1.Parameter change visualization:

Before:

After:

2.Fix actuator_controls_1 torque plot not showing due to incorrect topic instance selection.

Before:

After:

[bkueng]

Nice.

Parameter change visualization:

PX4 already checks for identical parameter changes: https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/parameters/parameters.cpp#L431
However, it looks like the problem is that PX4 still flags it as unsaved (https://github.com/PX4/PX4-Autopilot/blob/main/src/lib/parameters/parameters.cpp#L441), which is what the logger then uses for reading the changed parameters.
I think we should rather change that on the PX4 side.
Can you test with this change in PX4 and see if there's no identical parameters in the log anymore?

diff --git a/src/lib/parameters/parameters.cpp b/src/lib/parameters/parameters.cpp
index 560d6eec82..772a5c2a9e 100644
--- a/src/lib/parameters/parameters.cpp
+++ b/src/lib/parameters/parameters.cpp
@@ -438,7 +438,7 @@ param_set_internal(param_t param, const void *val, bool mark_saved, bool notify_
     }

     if (user_config.store(param, new_value)) {
-        params_unsaved.set(param, !mark_saved);
+        params_unsaved.set(param, !mark_saved && param_changed);
         result = PX4_OK;

     } else {

Actuator controls plotting:

That makes sense. Can you squash the first 2 commits?

[mengchaoheng]

I think we should rather change that on the PX4 side.

That would be great.

Can you test with this change in PX4 and see if there's no identical parameters in the log anymore?

It looks great.

Before:

After:

Can you squash the first 2 commits?

I squashed the first two commits into one and dropped the last commit, since the issue was already fixed elsewhere.
Thanks for the review!

[mengchaoheng]

The request has been processed, please review. @bkueng

[bkueng]

Thanks for testing. Did you create a pull request to PX4 already?

There's a minor CI failure, the line is a bit too long:

plot_app/configured_plots.py:564:0: C0301: Line too long (127/100) (line-too-long)

[mengchaoheng]

Thanks for testing. Did you create a pull request to PX4 already?

Oh, there is a misunderstanding here, I thought px4 had been updated. I create now.

I have created the PR.

There's a minor CI failure, the line is a bit too long:

I have already used line breaks.

@bkueng

[bkueng]

Looks good