v0.3.1 with Saxon fully working

todo.md

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+# Roadmap: good next functions
+
+Near-term useful features:
+
+1. Engine UX polish
+  - Show “SaxonJS loading…” when the large compiler file is first loaded.
+  - Show compile time vs transform time separately.
+  - Cache compiled SEF by stylesheet hash to avoid recompiling unchanged XSLT.
+2. Parameters
+  - Add UI for xsl:param.
+  - Support string/number/boolean parameters first.
+  - Later support XPath expressions.
+3. Better diagnostics
+  - Convert SaxonJS compiler/runtime errors into editor diagnostics.
+  - Extract line/module info when available.
+  - Jump from diagnostic to editor line.
+4. Examples / templates
+  - Identity transform.
+  - Rename elements.
+  - Extract table.
+  - Namespace cleanup.
+  - Grouping example.
+  - XSLT 3.0 shallow-copy example.
+5. Project files
+  - Export/import a full local project JSON:
+'''XML input
+XSLT
+output
+engine
+examples/tests
+parameters'''
+  - No uploads needed.
+6. Test cases inside the app
+  - Multiple XML inputs per stylesheet.
+  - Expected output assertions.
+  - Diff expected vs actual.
+  - “Run all tests” button.
+7. Diff views
+  - XML input vs output.
+  - Previous output vs current output.
+  - Pretty XML diff.
+8. Explain mode
+  - Start with static analysis:
+'''template match → output node candidates'''
+  - Later add instrumentation around generated SEF or stylesheet templates.
+9. Performance
+  - Web Worker for SaxonJS compile/transform.
+  - Prevent UI lockups on large XML.
+  - Progress indicator and cancellation if possible.
+10. Storage
+  - LocalStorage for small projects.
+  - IndexedDB for larger documents and histories.