test(semantic): add Optional/Result pattern matching test fixtures (#482)

10 new test fixtures covering:
- match_optional_0001/0002: basic Optional Some/None matching
- match_optional_nested_0001: nested logic within match arms
- match_optional_exhaustive_0001: exhaustive Optional match (no wildcard)
- match_optional_error_0001: missing None case produces SPY0266
- match_result_0001/0002: basic Result Ok/Err matching
- match_result_nested_0001: nested logic within Result match arms
- match_result_exhaustive_0001: exhaustive Result match (no wildcard)
- match_result_error_0001: missing Err case produces SPY0266

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: antonsynd

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_0001.expected

@@ -0,0 +1,2 @@
+value: 42
+none

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_0001.spy

@@ -0,0 +1,12 @@
+def describe(val: int?) -> str:
+    match val:
+        case Some(v):
+            return "value: " + str(v)
+        case None():
+            return "none"
+
+def main():
+    x: int? = Some(42)
+    y: int? = None()
+    print(describe(x))
+    print(describe(y))

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_0002.expected

@@ -0,0 +1,2 @@
+got: hello
+nothing

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_0002.spy

@@ -0,0 +1,12 @@
+def describe(val: str?) -> str:
+    match val:
+        case Some(s):
+            return "got: " + s
+        case _:
+            return "nothing"
+
+def main():
+    x: str? = Some("hello")
+    y: str? = None()
+    print(describe(x))
+    print(describe(y))

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_error_0001.error

@@ -0,0 +1 @@
+must return a value

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_error_0001.spy

@@ -0,0 +1,7 @@
+def describe(val: int?) -> str:
+    match val:
+        case Some(v):
+            return str(v)
+
+def main():
+    print(describe(Some(1)))

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_exhaustive_0001.expected

@@ -0,0 +1,2 @@
+42
+0

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_exhaustive_0001.spy

@@ -0,0 +1,10 @@
+def unwrap_or_default(val: int?) -> int:
+    match val:
+        case Some(v):
+            return v
+        case None():
+            return 0
+
+def main():
+    print(unwrap_or_default(Some(42)))
+    print(unwrap_or_default(None()))

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_nested_0001.expected

@@ -0,0 +1,3 @@
+big: 42
+small: 5
+none

src/Sharpy.Compiler.Tests/Integration/TestFixtures/pattern_matching/match_optional_nested_0001.spy

@@ -0,0 +1,13 @@
+def outer(val: int?) -> str:
+    match val:
+        case Some(v):
+            if v > 10:
+                return "big: " + str(v)
+            return "small: " + str(v)
+        case None():
+            return "none"
+
+def main():
+    print(outer(Some(42)))
+    print(outer(Some(5)))
+    print(outer(None()))