MVP: AILang-Sprache mit JSON-AST, Typchecker, LLVM-IR-Backend

Erste lauffähige Iteration. examples/sum.ail.json wird zu nativem Binary
kompiliert und druckt 55 (Summe 1..10) als End-to-End-Test.

Architektur:
- ailang-core: hashbares JSON-AST + canonical-form + pretty-printer
- ailang-check: monomorpher HM-Subset + Effekt-Set-Tracking
- ailang-codegen: LLVM-IR-Text-Emitter (kein libllvm-link)
- ail: CLI mit check/manifest/render/describe/emit-ir/build/builtins

Designentscheidungen sind in docs/DESIGN.md dokumentiert; der Verlauf
in docs/JOURNAL.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

examples/sum.ail.json

@@ -0,0 +1,76 @@
+{
+  "schema": "ailang/v0",
+  "name": "sum",
+  "imports": [],
+  "defs": [
+    {
+      "kind": "fn",
+      "name": "sum",
+      "type": {
+        "k": "fn",
+        "params": [{ "k": "con", "name": "Int" }],
+        "ret": { "k": "con", "name": "Int" },
+        "effects": []
+      },
+      "params": ["n"],
+      "doc": "rekursive Summe 0..=n",
+      "body": {
+        "t": "if",
+        "cond": {
+          "t": "app",
+          "fn": { "t": "var", "name": "==" },
+          "args": [
+            { "t": "var", "name": "n" },
+            { "t": "lit", "lit": { "kind": "int", "value": 0 } }
+          ]
+        },
+        "then": { "t": "lit", "lit": { "kind": "int", "value": 0 } },
+        "else": {
+          "t": "app",
+          "fn": { "t": "var", "name": "+" },
+          "args": [
+            { "t": "var", "name": "n" },
+            {
+              "t": "app",
+              "fn": { "t": "var", "name": "sum" },
+              "args": [
+                {
+                  "t": "app",
+                  "fn": { "t": "var", "name": "-" },
+                  "args": [
+                    { "t": "var", "name": "n" },
+                    { "t": "lit", "lit": { "kind": "int", "value": 1 } }
+                  ]
+                }
+              ]
+            }
+          ]
+        }
+      }
+    },
+    {
+      "kind": "fn",
+      "name": "main",
+      "type": {
+        "k": "fn",
+        "params": [],
+        "ret": { "k": "con", "name": "Unit" },
+        "effects": ["IO"]
+      },
+      "params": [],
+      "body": {
+        "t": "do",
+        "op": "io/print_int",
+        "args": [
+          {
+            "t": "app",
+            "fn": { "t": "var", "name": "sum" },
+            "args": [
+              { "t": "lit", "lit": { "kind": "int", "value": 10 } }
+            ]
+          }
+        ]
+      }
+    }
+  ]
+}