Delta A of the coordinated landing. The synthesis-only inference lock
(2026-05-28, docs/impl/type-system/inference.md) closes the door on
pulling a type inward from the surrounding context. The TY3 v0 impl
shipped with an ExpectedReturn binding source and an Option<&Ty>
threaded through the walker; both are now removed.

Walker (ck_types/src/check.rs):
- synth_with_expected dropped; synth is the one entry point.
- The Option<&Ty> parameter is gone from synth_uncached, synth_call,
  synth_generic_call, synth_block. Every expression synthesizes from its
  own text; the boundary (check / argument-vs-parameter) asserts the
  assignability relation against the synth.
- check() no longer special-cases bare Int literals against fixed-width
  expected pins. Per the lock, a bare numeric literal *always*
  synthesizes its default (Int / F64); the only path to a fixed-width
  value is a turbofish at the literal site. (TY2's locked open item.)
- collect_arg_bindings uses synth, not synth_with_expected.
- synth_block's tail synths plain; no expected threaded to the
  trailing expression for "tail call pinning from declared return."
- CallSite.expected_span field removed (it only fed the
  ExpectedReturn secondary).

Instantiation (ck_types/src/instantiate.rs):
- BindingOrigin::ExpectedReturn variant removed; the binding map now
  carries Argument origins only (Turbofish lands in Delta C).
- Module doc rewritten: two sources, in order — turbofish then
  arguments. The expected-return entry is gone; an explicit paragraph
  cites the synthesis-only lock and the redirect "turbofish at the
  call site" remediation.

Diagnostics (ck_types/src/diag.rs):
- source_phrase / source_label drop the ExpectedReturn arm. E0706's
  doc comment retargets at "(turbofish or arguments)".

Tests: 720 passed. Clippy: 0 warnings. Doc-link checker: 0 missing
anchors.

No fixture surgery needed: conflicting_bindings.cktest's expected
diagnostic already names the two argument sources ("Int from argument
1, String from argument 2"); the post-substitution E0702 cascade still
fires.

@@ -0,0 +62,4 @@
+    /// (`Maybe::None`) when this is 0; a payload-bearing variant is a
+    /// generic record in TY6.
+    #[must_use]
+    pub fn payload_arity(self) -> usize {

@@ -0,0 +76,4 @@
+        .into_iter()
+        .map(|tref| lift_required_type_ref(tref, src, scope, interner, caller_generics))
+        .collect();
+    expand_data_type(parent, &pinned, interner).unwrap_or_else(|| Ty::nominal(vid, Vec::new()))