fix: Add gerber test fixture to git, unblock CI

The .gitignore had *.gbr which prevented tests/fixtures/sample_top_copper.gbr
from being committed. Added exceptions for test fixture files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: RFingAdam

.gitignore

@@ -54,6 +54,10 @@ htmlcov/
 *.gbr
 *.drl
 *.ger
+# Allow test fixtures
+!tests/fixtures/*.gbr
+!tests/fixtures/*.drl
+!tests/fixtures/*.ger
 
 # Design review outputs (customer-specific, do not commit)
 /*.docx

tests/fixtures/sample_top_copper.gbr

@@ -0,0 +1,42 @@
+G04 Synthetic test Gerber - Top Copper Layer*
+G04 Generated for PCB EMCopilot parser tests*
+%TF.GenerationSoftware,SyntheticTestGen,1.0*%
+%TF.CreationDate,2025-01-15T12:00:00+00:00*%
+%TF.ProjectId,TestBoard,abc123,1.0*%
+%TF.FileFunction,Copper,L1,Top*%
+%TF.FilePolarity,Positive*%
+%FSLAX34Y34*%
+%MOMM*%
+%ADD10C,0.1500*%
+%ADD11C,0.2000*%
+%ADD12C,0.2500*%
+%ADD13R,0.6000X0.2000*%
+%ADD14C,0.6000*%
+%ADD15R,1.0000X1.0000*%
+D10*
+X00000000Y00150000D02*
+X00100000Y00150000D01*
+X00100000Y00150000D02*
+X00250000Y00150000D01*
+D10*
+X00000000Y00160000D02*
+X00100000Y00160000D01*
+X00100000Y00160000D02*
+X00250000Y00160000D01*
+D11*
+X00250000Y00150000D02*
+X00150000Y00080000D01*
+X00150000Y00080000D02*
+X00200000Y00120000D01*
+D12*
+X00200000Y00150000D02*
+X00250000Y00150000D01*
+D14*
+X00150000Y00080000D03*
+X00300000Y00150000D03*
+X00200000Y00250000D03*
+D15*
+X00400000Y00250000D03*
+X00350000Y00200000D03*
+G04 End of file*
+M02*