static value types via KnownValueType + single-param unwrap

[colinrozzi]

static value types via KnownValueType + single-param unwrap

Two related fixes for typed actor state in Theater.

KnownValueType trait: provides ValueType at the type level, so empty
containers (Vec, Option, BTreeSet, BTreeMap, [T; N], Result) carry
correct elem_type / inner_type info even when the value is empty.
Previously From<Vec> inferred elem_type from the items and defaulted
to S32 for empty Vecs, so an empty list field encoded as
list and theater's host-side type validator rejected it.

GraphValue derive emits KnownValueType impls for structs (Record),
tuple structs (Tuple), unit structs (Unit), and variants (Variant).
Pack's host-side PackType collapses to a blanket impl over Into

• KnownValueType, removing two parallel trait hierarchies.

Export macro single-param unwrap: a guest function with one typed
parameter (e.g. fn list(state: RouterState) -> ...) was decoding the
incoming value directly via try_into(). But theater always wraps inputs
as Tuple([...args]), so the wasm side received Tuple([state]) and
failed with 'failed to convert parameter'. The state-mode and
multi-param branches already unwrapped the wrapping tuple; the
single-param branch now does too.