Fix race condition in FontManager scaledFaces map

[adcondev]

Fixed a race condition in pkg/emulator/fonts.go where scaledFaces map was accessed without synchronization.
Added sync.RWMutex to FontManager struct and protected all accesses to scaledFaces.
Implemented double-checked locking in GetOrCreateScaledFace for thread-safe cache population.
Ensured font.Face resources are closed when evicted or discarded to prevent leaks.
Added a regression test TestScaledFacesRace.

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PR created automatically by Jules for task 11490920620544650492 started by @adcondev

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⚡ Benchmark Results

📈 Performance Comparison

📊 Click to expand detailed results

Current Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3117 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3654206	       327.8 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  405218	      2707 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  532221	      2059 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  518594	      2300 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   94836	     12634 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  426663	      2717 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  276552	      4161 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  528488	      2105 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  231340	      4783 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8838931	       135.4 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6696802	       177.7 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	362982424	         3.241 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	31875718	        38.24 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14612720	        82.62 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  501556	      2384 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  141553	      8442 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     620	   1863474 ns/op	 3469936 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     326	   3642526 ns/op	 5481085 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     140	   8483722 ns/op	 5235274 B/op	  230723 allocs/op

Base Branch Results

BenchmarkNewDocument-4    	1000000000	         0.3120 ns/op	       0 B/op	       0 allocs/op
BenchmarkBuildSimple-4    	 3624811	       331.4 ns/op	     240 B/op	       4 allocs/op
BenchmarkBuildComplex-4   	  418526	      2704 ns/op	    1809 B/op	      25 allocs/op
BenchmarkToJSON-4         	  532363	      2068 ns/op	     592 B/op	       3 allocs/op
BenchmarkParseDocument_Minimal-4    	  502388	      2308 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Receipt-4    	   95671	     12720 ns/op	    2392 B/op	      34 allocs/op
BenchmarkCommandUnmarshal_Text-4    	  429228	      2676 ns/op	     568 B/op	      19 allocs/op
BenchmarkCommandUnmarshal_Table-4   	  278497	      4143 ns/op	     944 B/op	      21 allocs/op
BenchmarkTextCommandParsing-4       	  539864	      2101 ns/op	     544 B/op	      16 allocs/op
BenchmarkTableCommandParsing-4      	  246220	      4786 ns/op	    1000 B/op	      29 allocs/op
BenchmarkParseHexString-4           	 8797804	       135.3 ns/op	      48 B/op	       2 allocs/op
BenchmarkCleanHexString-4           	 6661963	       178.0 ns/op	      64 B/op	       2 allocs/op
BenchmarkContainsSequence-4         	368543936	         3.311 ns/op	       0 B/op	       0 allocs/op
BenchmarkCheckCriticalCommands-4    	36582168	        38.96 ns/op	       0 B/op	       0 allocs/op
BenchmarkDocument_Validate-4       	14491092	        83.19 ns/op	       0 B/op	       0 allocs/op
BenchmarkParseDocument_Simple-4    	  502436	      2381 ns/op	     568 B/op	      14 allocs/op
BenchmarkParseDocument_Complex-4   	  138806	      8434 ns/op	    1352 B/op	      26 allocs/op
BenchmarkPrintImage_Small-4             	     586	   1915481 ns/op	 3469938 B/op	      24 allocs/op
BenchmarkPrintImage_Medium-4            	     328	   3669982 ns/op	 5481087 B/op	      24 allocs/op
BenchmarkPrintImage_ThermalPreview-4    	     140	   8658248 ns/op	 5235270 B/op	  230723 allocs/op

💡 Note: Use benchstat for statistical comparison

🎯 Summary

• Total Benchmarks: 32
• Average Speed: 2578131 ns/op
• Average Memory: 2396933 B/op
• Average Allocations: 41093 allocs/op