Implement basic IK in python for a single leg

[anton-matosov]

Follow the guide from https://oscarliang.com/inverse-kinematics-and-trigonometry-basics/ to implement the IK for a single leg
Deviations:

• use direct cosine rule formulas to make it easier to spot
• add safe_acos to easily detect non solvable solutions
• the Y coordinate in the leg IK for alpha and beta is a projection, not a real Y. Use L1 as the value for it
• Z_offset is simply a -z
• Use right hand side coordinates to match ROS (X forward, Y to the left, Z up)
• Use gamma as angle to X, this way it matches directly to joint angle

Add TF broadcast for the mathematical model joints and target location
Implement a bunch of test sequences
Calculate positions from angles with appropriate corrections for Dr.QP legs that have offset joints
Send calculated positions to /pose_async
Break if non solvable and don't send pose

[anton-matosov]

Video converted with

  ffmpeg \
  -i "drqp-2025-03-11-13-00-17.mkv" \
  -r 15 \
  -vf "scale=1024:-1,split[s0][s1];[s0]palettegen[p];[s1][p]paletteuse" \
  "drqp-2025-03-11-13-00-17.gif"

[codecov]

Codecov Report

Attention: Patch coverage is 8.36653% with 230 lines in your changes missing coverage. Please review.

Project coverage is 51.69%. Comparing base (0fc5417) to head (a67fe3d).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...ckages/runtime/drqp_brain/drqp_brain/one_leg_ik.py	0.00%	227 Missing ⚠️
packages/runtime/drqp_brain/setup.py	0.00%	3 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (0fc5417) and HEAD (a67fe3d). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (0fc5417)	HEAD (a67fe3d)
unittests-amd64	2	1
unittests-arm64	2	1

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #124      +/-   ##
==========================================
- Coverage   57.30%   51.69%   -5.62%     
==========================================
  Files          72       77       +5     
  Lines        1937     2188     +251     
  Branches       64       86      +22     
==========================================
+ Hits         1110     1131      +21     
- Misses        803     1033     +230     
  Partials       24       24              

Flag	Coverage Δ
unittests-amd64	51.69% <8.36%> (-5.62%)	⬇️
unittests-arm64	51.69% <8.36%> (-5.62%)	⬇️

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

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

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.