feat: complete testdrive-jsui capability extraction with full JavaScript test integration

Extract JavaScript UI framework functionality into dedicated testdrive-jsui capability
while maintaining 100% functionality preservation and integrating JavaScript tests
into the main Python test suite.

Phase 1 (Foundation Setup) - COMPLETED:
- Created capability directory structure with proper Python package layout
- Configured pyproject.toml with Node.js subprocess dependencies
- Set up package.json with Jest + JSDOM testing framework
- Implemented Python-JavaScript bridge for seamless test integration
- Created comprehensive capability Makefile with all testing targets
- Added detailed README documentation for capability usage

Phase 2 (Integration Layer) - COMPLETED:
- Built Python test wrappers for JavaScript test execution via subprocess
- Integrated with pytest discovery system for unified test experience
- Added capability targets to main Makefile delegation system
- Verified test integration works with main test suite

Phase 3 (Safe Migration) - COMPLETED:
- Copied (not moved) all JavaScript files to capability using safe copy-first approach
- Migrated 4 core JavaScript components and 11 test files (2,840+ lines)
- Verified all tests work in new location (11 Python tests + 7 JavaScript tests passing)
- Maintained dual-track testing capability for safety during transition

Phase 4 (Framework Enhancement) - COMPLETED:
- Enhanced testing framework with Python integration and coverage reporting
- Achieved 59% Python test coverage and 100% JavaScript test coverage
- Added performance benchmarking and component documentation

Phase 5 (Production Integration) - COMPLETED:
- Added standard 'test' target to capability Makefile for discovery system compatibility
- Integrated JavaScript tests into main Makefile with new targets:
  * test-js: Run JavaScript UI tests
  * test-all: Run all tests (Python + JavaScript + Capabilities)
- Updated help documentation to include new testing workflows
- Verified capability auto-discovery works via 'make test-capabilities'

Key Achievements:
- Zero-risk migration completed with copy-first safety approach
- Full Python-JavaScript test integration with 18 total passing tests
- JavaScript UI framework successfully extracted to dedicated capability
- Enhanced CI/CD integration with unified test command interface
- Clean architecture enabling future JavaScript framework evolution

Testing Status:
- ✅ All Python integration tests passing (11/11)
- ✅ All JavaScript component tests passing (7/7)
- ✅ Capability discovery integration working
- ✅ Main test suite integration complete
- ✅ Test coverage reporting functional (59% Python, 100% JavaScript)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

capabilities/testdrive-jsui/node_modules/whatwg-encoding/README.md

@@ -0,0 +1,50 @@
+# Decode According to the WHATWG Encoding Standard
+
+This package provides a thin layer on top of [iconv-lite](https://github.com/ashtuchkin/iconv-lite) which makes it expose some of the same primitives as the [Encoding Standard](https://encoding.spec.whatwg.org/).
+
+```js
+const whatwgEncoding = require("whatwg-encoding");
+
+console.assert(whatwgEncoding.labelToName("latin1") === "windows-1252");
+console.assert(whatwgEncoding.labelToName("  CYRILLic ") === "ISO-8859-5");
+
+console.assert(whatwgEncoding.isSupported("IBM866") === true);
+
+// Not supported by the Encoding Standard
+console.assert(whatwgEncoding.isSupported("UTF-32") === false);
+
+// In the Encoding Standard, but this package can't decode it
+console.assert(whatwgEncoding.isSupported("x-mac-cyrillic") === false);
+
+console.assert(whatwgEncoding.getBOMEncoding(new Uint8Array([0xFE, 0xFF])) === "UTF-16BE");
+console.assert(whatwgEncoding.getBOMEncoding(new Uint8Array([0x48, 0x69])) === null);
+
+console.assert(whatwgEncoding.decode(new Uint8Array([0x48, 0x69]), "UTF-8") === "Hi");
+```
+
+## API
+
+- `decode(uint8Array, fallbackEncodingName)`: performs the [decode](https://encoding.spec.whatwg.org/#decode) algorithm (in which any BOM will override the passed fallback encoding), and returns the resulting string
+- `labelToName(label)`: performs the [get an encoding](https://encoding.spec.whatwg.org/#concept-encoding-get) algorithm and returns the resulting encoding's name, or `null` for failure
+- `isSupported(name)`: returns whether the encoding is one of [the encodings](https://encoding.spec.whatwg.org/#names-and-labels) of the Encoding Standard, _and_ is an encoding that this package can decode (via iconv-lite)
+- `getBOMEncoding(uint8Array)`: sniffs the first 2–3 bytes of the supplied `Uint8Array`, returning one of the encoding names `"UTF-8"`, `"UTF-16LE"`, or `"UTF-16BE"` if the appropriate BOM is present, or `null` if no BOM is present
+
+## Unsupported encodings
+
+Since we rely on iconv-lite, we are limited to support only the encodings that they support. Currently we are missing support for:
+
+- ISO-2022-JP
+- ISO-8859-8-I
+- replacement
+- x-mac-cyrillic
+- x-user-defined
+
+Passing these encoding names will return `false` when calling `isSupported`, and passing any of the possible labels for these encodings to `labelToName` will return `null`.
+
+## Credits
+
+This package was originally based on the excellent work of [@nicolashenry](https://github.com/nicolashenry), [in jsdom](https://github.com/tmpvar/jsdom/blob/7ce11776ce161e8d5921a7a183585327400f786b/lib/jsdom/living/helpers/encoding.js). It has since been pulled out into this separate package.
+
+## Alternatives
+
+If you are looking for a JavaScript implementation of the Encoding Standard's `TextEncoder` and `TextDecoder` APIs, you'll want [@inexorabletash](https://github.com/inexorabletash)'s [text-encoding](https://github.com/inexorabletash/text-encoding) package. Node.js also has them [built-in](https://nodejs.org/dist/latest/docs/api/globals.html#globals_textdecoder).