Support some, ok and err wrappers and untyped function inputs

Track the LScript changes since the grammar was first written:

- some, ok and err are reserved prefix operators and wrapper patterns;
  the old |.some/|.ok/|.err forms and postfix/prefix ! are rejected
- function literal inputs may omit their type annotation, and tuple
  components may omit theirs; an empty typed tuple pattern is now just
  the unit pattern
- migrate fixtures, corpus, queries, CST contract and Rust tests

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/fixtures/valid/standard_signatures.ls

@@ -0,0 +1,19 @@
+use math.{pi, sqrt}
+use math as m
+use random.{Pcg32, pcg32, draw_u32}
+use time.{Duration, TimeError, duration_neg}
+use time as t
+
+circle: f64: pi
+root: f64: 4.0->sqrt
+# Host overloads are selected by the operand, so the literal is typed first.
+nine: f32: 9.0
+qualified_root: f32: nine->m.sqrt
+qualified_pi: f32: m.pi
+
+seed: u64: 42
+generator: Pcg32: seed->pcg32
+draw: u32: generator->draw_u32
+
+negate: Duration => Duration ! TimeError: duration_neg
+qualified_negate: t.Duration => t.Duration ! t.TimeError: t.duration_neg