Add XIC v1 Engine — Execute-In-Compressed Runtime Integration

- Implemented XIC loader, VM, ops, and executor
- Wired RUN_PROMPT directly to execute_gx() (no stubs)
- Added demo compressed model and demo XIC program
- Integrated XIC into glyph_runner.py with --xic flag and shell support
- Added full validation suite and XIC_INTEGRATION_REPORT.md
- Verified real GSZ3 decompression and execution pipeline

This commit introduces a complete compressed-space execution engine
with zero breaking changes and full backward compatibility.

programs/demo_chat.gx.json

@@ -0,0 +1,16 @@
+{
+  "magic": "GXIC1",
+  "version": 1,
+  "model": "programs/hello_model.gx",
+  "entrypoint": "main",
+  "symbols": {
+    "main": 0
+  },
+  "instructions": [
+    { "op": "LOAD_MODEL", "args": ["programs/hello_model.gx"] },
+    { "op": "SET_MODE", "args": ["chat"] },
+    { "op": "SET_PARAM", "args": ["temperature", 0.2] },
+    { "op": "SET_PARAM", "args": ["trace", false] },
+    { "op": "RUN_PROMPT", "args": ["Hello from XIC inside compressed space."] }
+  ]
+}