Post-merge-review: add missing tests from ember-template-lint test suite

[johanrd]

Summary

Systematic comparison of all 134 template rules against the ember-template-lint test suite. 15 rules had missing test coverage.

Tests added

Rule	Test added	ember-template-lint reference
template-no-nested-interactive	ignoreUsemapAttribute option alias	no-nested-interactive-test.js
template-no-curly-component-invocation	requireDash: true with single-word named-arg call	no-curly-component-invocation-test.js
template-no-abstract-roles	All 10 abstract roles not previously tested (composite, input, landmark, range, roletype, section, sectionhead, select, structure, window)	no-abstract-roles-test.js
template-no-obsolete-elements	8 additional obsolete elements in GJS tester (big, blink, center, font, frame, frameset, strike, tt)	no-obsolete-elements-test.js
template-self-closing-void-elements	require config option — all void elements, valid and invalid with fixer output	self-closing-void-elements-test.js
template-no-invalid-interactive	additionalInteractiveTags and ignoredTags config options	no-invalid-interactive-test.js
template-no-aria-hidden-body	Boolean aria-hidden attribute without value	no-aria-hidden-body-test.js
template-no-invalid-role	catchNonexistentRoles config option	no-invalid-role-test.js
template-require-strict-mode	Class-based GJS component valid case	require-strict-mode-test.js
template-link-rel-noopener	target="_self" valid case; full HBS tester section	link-rel-noopener-test.js
template-no-element-event-actions	requireActionHelper config option (true and false)	no-element-event-actions-test.js
template-no-array-prototype-extensions	String literal paths in get helper; plain-text and string-attr false-positive checks; lastObject in named hash arg	no-array-prototype-extensions-test.js
template-no-duplicate-landmark-elements	popover element scoping in GJS tester	no-duplicate-landmark-elements-test.js
template-no-accesskey-attribute	Boolean accesskey attribute, dynamic mustache value, and concat string attribute	no-accesskey-attribute-test.js

Implementation gaps evaluated

Three behaviors in ember-template-lint were found to have no equivalent tests or implementation in this plugin. Each was investigated and a decision made:

Rule	Missing behavior	Decision
template-no-forbidden-elements	filePath-based element exceptions (head.hbs)	Skip — ember-cli-head is a classic-Ember-only addon; not relevant to GJS/GTS
template-no-implicit-this	regex patterns in allow array	Shipped — see PR #2707
template-no-bare-strings	false config to disable the rule	Skip — use "off" in ESLint config instead; false is not idiomatic in ESLint

Test plan

• npm test — all tests pass