test: add unit tests for P1-P5 paper integration modules

Add 134 unit tests covering the new modules introduced by the
LLM-paper integration tracks:

- agent_scaffold_tests.rs (17 tests): CallGraphBuilder, FunctionLookup,
  call-graph path sampling for C and Python
- agent_flow_tests.rs (35 tests): TypeError Display, typecheck,
  diagnoser, DSL harness construction, apply_rewrite
- context_pacvd_tests.rs (53 tests): AbstractionLevel, extract,
  auto_level, 4-dimensional abstraction vectors
- rulesynth_validator_tests.rs (35 tests): validate, format_feedback,
  load_corpus, emit_yaml, Pattern construction

Fix two production bugs discovered by the C tests: get_function_name
in both fn_lookup.rs and call_graph_paths.rs did not recognise
tree-sitter-c's function_declarator node kind, so C functions were
never indexed. Add 'function_declarator' to the matched child kinds.

CI gate: fmt OK, clippy clean, 2944 tests pass (+134).

Author: Mte90

src/agent_scaffold/call_graph_paths.rs

@@ -277,7 +277,10 @@ fn get_function_name(node: &tree_sitter::Node, source: &[u8]) -> Option<String>
         }
 
         // Python/Rust function_definition with name child
-        if child_kind == "function_definition" || child_kind == "declarator" {
+        if child_kind == "function_definition"
+            || child_kind == "declarator"
+            || child_kind == "function_declarator"
+        {
             for name_child in child.children(&mut child.walk()) {
                 if name_child.kind() == "identifier" {
                     return name_child.utf8_text(source).ok().map(|s| s.to_string());

src/agent_scaffold/fn_lookup.rs

@@ -229,7 +229,10 @@ fn get_function_name(node: &tree_sitter::Node, source: &[u8]) -> Option<String>
         }
 
         // Python/Rust function_definition with name child
-        if child_kind == "function_definition" || child_kind == "declarator" {
+        if child_kind == "function_definition"
+            || child_kind == "declarator"
+            || child_kind == "function_declarator"
+        {
             for name_child in child.children(&mut child.walk()) {
                 if name_child.kind() == "identifier" {
                     return name_child.utf8_text(source).ok().map(|s| s.to_string());