fix(examples): resolve --output against the working directory in three render paths

[TMHSDigital]

Summary

Closes #222. damped-track-aim, gn-sdf-remesh and turntable passed --output straight to scene.render.filepath. Blender resolves a relative path against the blend-file directory; a --background run has no .blend, so the path resolves against the drive root. Their documented commands (-- --output aim.png …) wrote to C:\ and exited non-zero. The fix is path = os.path.abspath(path) before the assignment, as every other example already does.

Type

• feat
• fix — broken documented render command
• docs / chore / ci / refactor

Evidence

• live-run-proven with E:\Blender-Developer-Tools\.scratch\blender-5.2.1-windows-x64\blender.exe (reports Blender 5.2.1 LTS) and ...\blender-4.5.11-windows-x64\blender.exe (reports Blender 4.5.11 LTS):

  Script	Before (relative --output, 5.2.1)	After, 5.2.1	After, 4.5.11
  damped_track_aim	exit 10, Saved: 'C:\.scratch\...'	exit 0, file in cwd	exit 0, file in cwd
  gn_sdf_remesh	exit 4, Saved: 'C:\.scratch\relprobe\...'	exit 0, file in cwd	exit 0, file in cwd
  turntable	exit 4, Saved: 'C:\.scratch\relprobe\...'	exit 0, file in cwd	exit 0, file in cwd

  After the fix, nothing is written under C:\.scratch\.

• The "before" column is the falsification: the relative-path failure is reproducible without the fix and gone with it.

• Check path unchanged: the edit is inside render_still only. Smoke never passes --output to these three; this PR's smoke jobs cover the check path.

Checklist

• Explicit paths only.
• Counts and manifest unchanged; no gallery change (render content unchanged).
• Failure reproduced before and gone after (above).
• DCO Signed-off-by: present.
• No credentials or emails. Binary paths are as the template asks.

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