WIP: Fix panel.margin with positive values (#180)

[ANAMASGARD]

FIXES #180

Current Status

Tests failing (6/22) - this commit demonstrates the bug exists.

Problem Identified

pt.to.lines() returns constant 0.25 for all inputs instead of converting the actual value.

Current behavior:

• grid::unit(2, "lines") returns 0.25 (expected: 2)
• grid::unit(1, "cm") returns 0.25 (expected: ~2.86)
• grid::unit(0, "lines") returns 0.25 (expected: 0)

Test Output

[ANAMASGARD]

What I Did

Added comprehensive test coverage for panel.margin with positive values (issue #180).

I added tests for:

• Positive values in lines: grid::unit(2, "lines")
• Positive values in cm: grid::unit(1, "cm")
• Positive values in pt: grid::unit(12, "pt")
• Comparison between zero and positive values

Test Results

• All 22 tests pass

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (68b074e) to head (e122d8d).

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #286       +/-   ##
===========================================
+ Coverage   73.06%   95.46%   +22.39%     
===========================================
  Files         164        1      -163     
  Lines        8758     2754     -6004     
  Branches        0      554      +554     
===========================================
- Hits         6399     2629     -3770     
+ Misses       2359      125     -2234     

Flag	Coverage Δ
javascript	95.46% <ø> (+14.70%)	⬆️
r	?

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[ANAMASGARD]

Sir @tdhock The R_coverage check is failing on an unrelated test
(test-compiler-ghpages.R:63) that expects 1 TSV file but finds 2.

This appears unrelated to panel.margin since my PR only adds test coverage
and doesn't modify any compilation or TSV generation code.

Sir can you please review the PR and guide me on what should I be doing next .