Release v0.4.2

[roncodes]

Patch release for v0.4.2: restores the hidden state of every Attach::Tooltip and Attach::Popover in production builds. The sitting release (component playground, signature pad, coverage) moved to release/v0.4.3 / #177 so this ships first.

What broke

v0.4.1 (#176, 434196f) started forwarding the host's browser targets to postcss-preset-env. With the console's targets (last 1 Chrome/Firefox/Safari versions) the preset skips the nesting-rules transform, because those browsers support nesting natively. The attacher styles that keep an attachment at opacity: 0 until it is shown are written nested, and ember-cli's production minifier (clean-css 5) cannot parse nesting: it emitted those rules as top-level & > .ember-attacher-fill selectors that match nothing, so every tooltip and popover rendered at full opacity without a hover. Development builds were unaffected because the browser parsed the nested block itself, which is why it reached production.

The popover component itself is not at fault; its v0.4.1 changes only affect interactive attachments.

Fix

• lib/postcss-options.js: postcssPresetEnv({ …, features: { 'nesting-rules': true } }) so nesting is always flattened, whatever the targets.
• tests/node/postcss-build-test.cjs: compiles attacher.css for the console's targets, asserts the flat hide rule is present with no & left, then minifies with the same clean-css ember-cli uses and asserts the rule survives. Fails on main, passes here.
• package.json → 0.4.2, RELEASE.md first line names v0.4.2 so release.yml tags on merge.

Verification

• node --test tests/node/postcss-build-test.cjs: 4 pass (the new test fails with the fix reverted).
• ember build --environment=production of the dummy app: the minified vendor CSS contains .ember-attacher[x-placement^=top]>.ember-attacher-fill{…;opacity:0} for all four placements and no nesting leftovers; before the fix the console's built vendor.css had only the nested form.