feat: unified testing framework — unit and e2e same syntax, seed-based graph testing, debugger infrastructure

- New crate el-test: test discovery, in-memory graph seeding, assertion evaluator, TestRunner, TestReport with human/JSON/JUnit XML output
- New keywords: test, seed, assert, target — fully integrated into lexer, parser, codegen, type-checker
- Parser extensions: TestDef, SeedStmt, Assert AST nodes; seed blocks handle type: as field name (keyword-as-ident in seed context)
- Debugger: DebugEvent, Debugger, StepMode, StackFrame in el-compiler — breakpoints, step-over, step-into, step-out
- CLI: el test-file <file.el> runs tests; el test integrates with project; el debug attaches debugger; --output json|junit for CI
- 52 new tests in el-test covering discovery, graph seeding, assertion evaluation, pass/fail/error/skip, report generation, JUnit XML
- Example: examples/hello-project/src/tests.el — 6 unit tests pass, 1 e2e test correctly skipped without ENGRAM_URL

examples/hello-project/src/tests.el

@@ -0,0 +1,57 @@
+// Engram language — example test file
+// Run with: el test-file examples/hello-project/src/tests.el
+
+test "basic arithmetic" {
+    let x: Int = 6
+    let y: Int = 7
+    let result: Int = x * y
+    assert result == 42
+}
+
+test "string operations" {
+    let greeting: String = "Hello"
+    let name: String = "Engram"
+    let full: String = greeting + ", " + name
+    assert full == "Hello, Engram"
+}
+
+test "type graph has Point type" {
+    seed Node {
+        type: "Point"
+        content: "A 2D coordinate"
+        importance: 0.8
+        tier: Semantic
+    }
+
+    let results = activate Point where "coordinate"
+    assert results.len() > 0
+}
+
+test "empty graph" {
+    let results = activate Customer where "anything"
+    assert results.len() == 0
+}
+
+test "empty graph returns insufficient" {
+    let result = reason("Is there a customer named Will?")
+    assert result.verdict == "Insufficient"
+}
+
+test "seeded graph reasoning" {
+    seed Node {
+        type: "Customer"
+        content: "Will Anderson, founding member"
+        importance: 0.9
+        tier: Semantic
+    }
+
+    let result = reason("founding member")
+    assert result.verdict == "Supported"
+}
+
+test "production customer lookup" target: e2e {
+    // No seeds — uses the real Engram database
+    // (skipped when ENGRAM_URL is not set)
+    let results = activate Customer where "founding member"
+    assert results.len() > 0
+}