Add Jest unit test suite for the GF-1 library

[devin-ai-integration]

Summary

The repo had no tests, no test runner and no CI: coverage of every module was 0%. JS/GF-1.js (~60 KB, 123 functions) is the whole library and was therefore the least covered module by far, so this PR adds a Jest + jsdom suite around it — 206 tests, 98% of its functions and 66% of its statements executed — plus a GitHub Actions workflow that runs it.

JS/GF-1.js is a plain browser script: every function is a top-level declaration and nothing is exported, so require()-ing it from a test yields an empty object. Rather than modifying the shipped source, tests/gf-transform.js is a Jest transformer that appends an export epilogue at transform time and delegates to babel-jest so Istanbul instrumentation (and thus the coverage report) still applies:

// tests/gf-transform.js
process(src, path, options) {
  const names = [...src.matchAll(/function\s+(_[A-Za-z0-9_]*)\s*\(/g)].map(m => m[1]);
  const epilogue = `;module.exports = { ${names}, _gData, _error_message, ...,
     setRunConsole: v => { run_console = v; } };`;
  return babelTransformer.process(src + epilogue, path, options);
}

The setRunConsole escape hatch lets tests/logging.test.js flip the library's run_console flag and assert on the _writeLog diagnostics, which are otherwise dead code.

Suites, by area of the library:

file	covers
tests/type-utils.test.js	_isArray, _isFunction, _isUndefined, _vardump, _cleanArray
tests/string-utils.test.js	_checkEmail, _isUrl, _escapeHtml, _moneyFormat, _replaceJS/_replaceMaster/_returnMaster, _charToDec/_decToChar, _randomStr/_randomInt, _encryptInt/_decryptInt round trip
tests/date.test.js	_getYear/_getMonth/_getDay/_getDate/_getDayName/_getMonthName/_getTime
tests/dom.test.js	_getById, _printTo, _clear, _setValue, _getValById/_getValByName, visibility helpers, _required, _qSelector*, _textStyle
tests/components.test.js	_addList, _addItemTable, _addOption/_getOption
tests/cookie-storage.test.js	_setCookie/_getCookie/_deleteCookie, _saveStorage/_getStorage (incl. the {id,status,token,ip,key} object form)
tests/events.test.js	click/key/mouse/focus/drag handlers, _keyArrow, _keyCustom, _onKeyUpToText, _rightClick
tests/ajax.test.js	_requestGET/POST/PUT/DELETE, _loadDoc, _checkInternet, _import against a fake XMLHttpRequest
tests/canvas.test.js	_drawCircle/_drawText/_drawLine/_drawImage/_clearCanvas against a stubbed 2d context
tests/window-location.test.js	_GET, _putUrl, _myUrl, _getHost, counters, _writeAlert, _animation, _confirm, _newTab/_newIframe, _writeLog
tests/browser-window.test.js	_detectBrowser, _openUrl/_refresh, _getLocation, _newForm/_print, _previewImage, scroll helpers
tests/logging.test.js	run_console diagnostic paths and the _gData class

Tests assert the library's current behaviour, including its quirks (e.g. _getCookie returns false when the requested cookie isn't the first one, _showMe sets visibility: block); no library code was changed, so nothing is fixed here — the suite pins today's behaviour so future changes are safe.

app.js and code/part-*.js are page-specific demo scripts bound to the documentation site's DOM ids, so they are excluded from collectCoverageFrom rather than tested.

Link to Devin session: https://app.devin.ai/sessions/1c87befeef8849768a3adcdc8d231ff2
Requested by: @lamhotsimamora

[devin-ai-integration]

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