AlwaysListMatcher::match_value always returns false, contradicting its own doc comment

\`AlwaysList\` is documented as "List that always matches." (\`engine/src/list_matcher.rs:80\`). Its
matcher, however, is byte-identical to \`NeverList\`'s — "List that never matches."
(\`engine/src/list_matcher.rs:111\`):

\`\`\`rust
// engine/src/list_matcher.rs:103-109
impl ListMatcher for AlwaysListMatcher {
fn match_value(&self, _: &str, _: &LhsValue<'_>) -> bool {
false
}
fn clear(&mut self) {}
}
\`\`\`

Per the doc comment this should return \`true\`.

**Reachability:** any scheme built with \`builder.add_list(ty, AlwaysList {})\` (Rust) or
\`wirefilter_add_always_list_to_scheme\` (\`ffi/src/lib.rs:303-306\`, the FFI equivalent), then a filter
using \`in \$listname\` against a field of that type.

**Impact:** a field typed against \`AlwaysList\` never matches — the opposite of its documented
behavior. No crash, no error, no signal anything is wrong.

Minimal repro:
\`\`\`rust
let mut builder = SchemeBuilder::new();
builder.add_field("num", Type::Int).unwrap();
builder.add_list(Type::Int, AlwaysList {}).unwrap();
let scheme = builder.build();

let ast = scheme.parse("num in \$numbers").unwrap();
let filter = ast.compile();
let mut ctx = ExecutionContext::new(&scheme);
ctx.set_field_value_from_name("num", 42).unwrap();
assert_eq!(filter.execute(&ctx).unwrap(), true); // fails: actually false
\`\`\`

**Suggested fix:** change the return value from \`false\` to \`true\`. Verified this doesn't break either
existing consumer — \`list_matcher.rs\`'s own test compares matcher identity, not match results, and
\`ast/visitor.rs\`'s tests only use \`AlwaysList\` to make a list name resolvable, never assert on match
outcomes. Happy to open this as a one-line PR with a regression test instead of an issue, if preferred.

Found with the [rust-in-peace](https://github.com/scadastrangelove/rust-in-peace) pipeline.

Open engine/src/list_matcher.rs and inspect AlwaysListMatcher alongside NeverList; the issue identifies the incorrect behavior and the expected result. Run the relevant Rust tests, then add a regression case for the provided scheme and filter example, verifying that the AlwaysList match succeeds without breaking existing matcher or visitor tests.

Written by the indexing model from the issue text.