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/html-encoding-sniffer/README.md

@@ -0,0 +1,40 @@
+# Determine the Encoding of a HTML Byte Stream
+
+This package implements the HTML Standard's [encoding sniffing algorithm](https://html.spec.whatwg.org/multipage/syntax.html#encoding-sniffing-algorithm) in all its glory. The most interesting part of this is how it pre-scans the first 1024 bytes in order to search for certain `<meta charset>`-related patterns.
+
+```js
+const htmlEncodingSniffer = require("html-encoding-sniffer");
+const fs = require("fs");
+
+const htmlBytes = fs.readFileSync("./html-page.html");
+const sniffedEncoding = htmlEncodingSniffer(htmlBytes);
+```
+
+The passed bytes are given as a `Uint8Array`; the Node.js `Buffer` subclass of `Uint8Array` will also work, as shown above.
+
+The returned value will be a canonical [encoding name](https://encoding.spec.whatwg.org/#names-and-labels) (not a label). You might then combine this with the [whatwg-encoding](https://github.com/jsdom/whatwg-encoding) package to decode the result:
+
+```js
+const whatwgEncoding = require("whatwg-encoding");
+const htmlString = whatwgEncoding.decode(htmlBytes, sniffedEncoding);
+```
+
+## Options
+
+You can pass two potential options to `htmlEncodingSniffer`:
+
+```js
+const sniffedEncoding = htmlEncodingSniffer(htmlBytes, {
+  transportLayerEncodingLabel,
+  defaultEncoding
+});
+```
+
+These represent two possible inputs into the [encoding sniffing algorithm](https://html.spec.whatwg.org/multipage/syntax.html#encoding-sniffing-algorithm):
+
+- `transportLayerEncodingLabel` is an encoding label that is obtained from the "transport layer" (probably a HTTP `Content-Type` header), which overrides everything but a BOM.
+- `defaultEncoding` is the ultimate fallback encoding used if no valid encoding is supplied by the transport layer, and no encoding is sniffed from the bytes. It defaults to `"windows-1252"`, as recommended by the algorithm's table of suggested defaults for "All other locales" (including the `en` locale).
+
+## Credits
+
+This package was originally based on the excellent work of [@nicolashenry](https://github.com/nicolashenry), [in jsdom](https://github.com/tmpvar/jsdom/blob/16fd85618f2705d181232f6552125872a37164bc/lib/jsdom/living/helpers/encoding.js). It has since been pulled out into this separate package.