[ty] Only consider a type T a subtype of a protocol P if all of P's members are fully bound on T (#18466)

## Summary

Fixes https://github.com/astral-sh/ty/issues/578

## Test Plan

mdtests

crates/ty_python_semantic/resources/mdtest/narrow/hasattr.md

@@ -26,7 +26,7 @@ def f(x: Foo):
     else:
         reveal_type(x)  # revealed: Foo
 
-def y(x: Bar):
+def g(x: Bar):
     if hasattr(x, "spam"):
         reveal_type(x)  # revealed: Never
         reveal_type(x.spam)  # revealed: Never
@@ -35,4 +35,25 @@ def y(x: Bar):
 
         # error: [unresolved-attribute]
         reveal_type(x.spam)  # revealed: Unknown
+
+def returns_bool() -> bool:
+    return False
+
+class Baz:
+    if returns_bool():
+        x: int = 42
+
+def h(obj: Baz):
+    reveal_type(obj)  # revealed: Baz
+    # error: [possibly-unbound-attribute]
+    reveal_type(obj.x)  # revealed: int
+
+    if hasattr(obj, "x"):
+        reveal_type(obj)  #  revealed: Baz & <Protocol with members 'x'>
+        reveal_type(obj.x)  # revealed: int
+    else:
+        reveal_type(obj)  # revealed: Baz & ~<Protocol with members 'x'>
+
+        # TODO: should emit `[unresolved-attribute]` and reveal `Unknown`
+        reveal_type(obj.x)  # revealed: @Todo(map_with_boundness: intersections with negative contributions)
 ```

crates/ty_python_semantic/src/types/instance.rs

@@ -4,7 +4,7 @@ use std::marker::PhantomData;
 
 use super::protocol_class::ProtocolInterface;
 use super::{ClassType, KnownClass, SubclassOfType, Type};
-use crate::symbol::{Symbol, SymbolAndQualifiers};
+use crate::symbol::{Boundness, Symbol, SymbolAndQualifiers};
 use crate::types::{ClassLiteral, TypeMapping, TypeVarInstance};
 use crate::{Db, FxOrderSet};
 
@@ -45,12 +45,12 @@ impl<'db> Type<'db> {
         protocol: ProtocolInstanceType<'db>,
     ) -> bool {
         // TODO: this should consider the types of the protocol members
-        // as well as whether each member *exists* on `self`.
-        protocol
-            .inner
-            .interface(db)
-            .members(db)
-            .all(|member| !self.member(db, member.name()).symbol.is_unbound())
+        protocol.inner.interface(db).members(db).all(|member| {
+            matches!(
+                self.member(db, member.name()).symbol,
+                Symbol::Type(_, Boundness::Bound)
+            )
+        })
     }
 }