Function phase_resolve_derived 

pub fn phase_resolve_derived(
    groups: &BTreeMap<String, Vec<usize>>,
    kinds: &BTreeMap<String, UnitKind>,
    parsed: &[ParsedFile],
    unit_tables: &mut HashMap<String, UnitTable>,
    errors: &mut ErrorSink,
)

S4a (#1966): resolve each derived capability (capability Sessions = Kv) against the capabilities its context flattens in with consumes U { Kv }, and record it. A valid one enters the unit’s capability table with its base’s operations, so every later check treats it as an ordinary capability; its provision is implied (the base’s platform provider, bound to the instance’s own Worker binding). Runs after crate::symbols::record_flattened_caps.