Fix sinusoidal_force_sensor build and runtime, set wave to 25 Hz

[mmmarinho]

Summary

Fixes the compilation error and the startup crash in the sinusoidal_force_sensor example, and sets the sinusoidal wave frequency to 25 Hz while keeping the 100 Hz publish rate.

Changes

All in src/examples/sinusoidal_force_sensor.cpp:

1. Compilation error — DQ force({value, 0.0, 0.0}) failed with static assertion failed: THIS_METHOD_IS_ONLY_FOR_VECTORS_OF_A_SPECIFIC_SIZE. The initializer list built a dynamic-size VectorXd, and Eigen's 3-scalar constructor requires a fixed-size vector. Now constructs from an explicit Vector3d:

   DQ force(Vector3d(value, 0.0, 0.0));
   DQ torque(Vector3d(0.0, value, 0.0));

2. std::bad_weak_ptr crash at startup — the constructor called shared_from_this() before the owning shared_ptr existed. main now builds the node first and then calls attach_server() (which creates the ForceSensorServer and timer), so shared_from_this() is valid.

3. 25 Hz wave at 100 Hz publish rate — separated the previously-conflated constants:

   const double frequency_hz  = 25.0;   // sine wave frequency
   const double tick_rate_hz  = 100.0;  // timer / publish rate

   The timer period and phase advance use tick_rate_hz; the sine uses frequency_hz/angular_frequency. Previously a 100 Hz wave sampled at 100 Hz aliased to ~0.

Verification

Verified in the repo's Docker environment (murilomarinho/sas:jazzy, same as CI):

• colcon build finishes cleanly (exit 0)
• Node starts without aborting; publishes on /sinusoidal_force_sensor/get/wrench
• Captured WrenchStamped samples show one full sine period every 4 ticks (40 ms → 25 Hz) with amplitude 2.0

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This PR was created by an AI agent (OpenHands) on behalf of the user.

[mmmarinho]

👍