At-rule preludes: every bare identifier is reported as a dependency (@keyframes, @media, @forward ... show)

Filing this as a generalisation of #14, which reports the `@use "x" as ns` case. The root cause looks identical, but the effect is broader than the `as` keyword: **any bare identifier appearing in an at-rule prelude is returned as a dependency**, including at-rules that can never carry an import.

## Reproduction

`detective-scss@5.0.2`, Node v24.13.0:

```js
const detective = require('detective-scss');

console.log(detective('@keyframes fade { from { opacity: 0 } }'));
// -> [ 'fade' ] expected: []

console.log(detective('@media screen and (min-width: 40px) { .a { color: red } }'));
// -> [ 'screen', 'and' ] expected: []

console.log(detective('@use "a" as c;'));
// -> [ 'a', 'as', 'c' ] expected: [ 'a' ] (this is #14)

console.log(detective('@use "a" as *;'));
// -> [ 'a', 'as' ] expected: [ 'a' ]

console.log(detective('@forward "a" show $b;'));
// -> [ 'a', 'show' ] expected: [ 'a' ]
```

Not affected, for contrast - their preludes carry no bare identifier at the top level:

```js
detective('@supports (display: grid) { .a { display: grid } }') // -> []
detective('@font-face { font-family: Foo; src: url(a.woff2) }') // -> []
detective('@use "a";') // -> [ 'a' ] correct
detective('@import "a";') // -> [ 'a' ] correct
```

## Why it matters downstream

`detective-scss` is reached through `precinct` -> `madge`. On a mid-sized Vue codebase (1014 files), `madge --circular` reports these phantom specifiers as unresolved dependencies on every run. They are not actionable: the only ways to silence them would be to stop using `@use ... as *` or to rename `@keyframes`, i.e. to degrade working stylesheets to satisfy the parser.

`@keyframes` is the most likely to bite, since animation names are arbitrary and plentiful. `@media` only shows up when the query uses the `screen and (...)` form rather than a bare parenthesised condition - which is probably why this has gone unnoticed.

## Suggested direction

`@import`, `@use` and `@forward` are the only at-rules that can introduce a dependency, and in each case the dependency is the **quoted string that immediately follows the at-rule name**. Restricting extraction to that position - rather than collecting identifier tokens from the whole prelude - would fix #14 and the cases above together.

Happy to test a patch against a real codebase if that helps.

Start at the detective-scss entry point and trace how at-rule preludes are scanned for dependencies. Add regression coverage for the @keyframes, @media, @use, and @forward examples, then run the existing test suite. Done means only the quoted dependency immediately following @import, @use, or @forward is reported, while the other shown cases return empty or expected results.

Written by the indexing model from the issue text.