chore: remove emscripten.rs platform from coverage, add html generation task, hide absolute path with remap-path-prefix, organize gitignore

Justfile

@@ -1,17 +1,32 @@
 set shell := ["bash", "-c"]
 set windows-shell := ["powershell.exe", "-NoLogo", "-Command"]
 
-coverage_exclude_pattern := "app.rs|audio.rs|error.rs"
+# Regex to exclude files from coverage report, double escapes for Justfile + CLI
+# You can use src\\\\..., but the filename alone is acceptable too
+coverage_exclude_pattern := "src\\\\app.rs|audio.rs|src\\\\error.rs|platform\\\\emscripten.rs"
+
+# !!! --ignore-filename-regex should be used on both reports & coverage testing
+# !!! --remap-path-prefix prevents the absolute path from being used in the generated report
+
+# Generate HTML report (for humans, source line inspection)
+html: coverage
+    cargo llvm-cov report \
+    --remap-path-prefix \
+    --ignore-filename-regex "{{ coverage_exclude_pattern }}" \
+    --html \
+    --open
 
 # Display report (for humans)
 report-coverage: coverage
     cargo llvm-cov report \
+    --remap-path-prefix \
     --ignore-filename-regex "{{ coverage_exclude_pattern }}"
 
 # Run & generate report (for CI)
 coverage:
     cargo llvm-cov \
     --lcov \
+    --remap-path-prefix \
     --ignore-filename-regex "{{ coverage_exclude_pattern }}" \
     --output-path lcov.info \
     --profile coverage \