feat: unused return value warnings, empty body fix, test consolidation

- Add compiler warning for unused return values (function called as
  statement when it returns a value)
- Fix panic in lower_code_block when function body reduces to empty stmts
- Consolidate e2e, evm-tests, and lexer test files into single binaries
  via main.rs + suites/ directories (~50 binaries → ~19)
- Fix clippy duplicate_mod in lexer test consolidation
- Add docs for external calls type spec

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

Author: brockelmore

crates/driver/src/compiler.rs

@@ -193,6 +193,11 @@ impl Compiler {
             CompileError::Aborted
         })?;
 
+        // Emit any warnings from IR lowering
+        for warning in &ir_program.warnings {
+            self.session.emit_warning(warning.clone());
+        }
+
         if emit == EmitKind::Ir || emit == EmitKind::PrettyIr {
             return Ok(CompileOutput {
                 tokens: None,
@@ -226,6 +231,7 @@ impl Compiler {
                     &edge_ir::EvmProgram {
                         contracts: vec![contract.clone()],
                         free_functions: Vec::new(),
+                        warnings: Vec::new(),
                     },
                     self.session.config.optimization_level,
                     self.session.config.optimize_for,
@@ -254,6 +260,7 @@ impl Compiler {
             let single_program = edge_ir::EvmProgram {
                 contracts: vec![contract.clone()],
                 free_functions: Vec::new(),
+                warnings: Vec::new(),
             };
             let bytecode = edge_codegen::compile(
                 &single_program,

crates/e2e/tests/main.rs

@@ -0,0 +1,46 @@
+#![allow(missing_docs)]
+
+#[path = "suites/access_exec.rs"]
+mod access_exec;
+#[path = "suites/calldata_args.rs"]
+mod calldata_args;
+#[path = "suites/counter.rs"]
+mod counter;
+#[path = "suites/erc20.rs"]
+mod erc20;
+#[path = "suites/examples.rs"]
+mod examples;
+#[path = "suites/expressions.rs"]
+mod expressions;
+#[path = "suites/features_exec.rs"]
+mod features_exec;
+#[path = "suites/finance_exec.rs"]
+mod finance_exec;
+#[path = "suites/generics_exec.rs"]
+mod generics_exec;
+#[path = "suites/generics_negative.rs"]
+mod generics_negative;
+#[path = "suites/inline_asm_exec.rs"]
+mod inline_asm_exec;
+#[path = "suites/packed_exec.rs"]
+mod packed_exec;
+#[path = "suites/packed_storage_exec.rs"]
+mod packed_storage_exec;
+#[path = "suites/packed_transient_exec.rs"]
+mod packed_transient_exec;
+#[path = "suites/patterns_exec.rs"]
+mod patterns_exec;
+#[path = "suites/tokens_exec.rs"]
+mod tokens_exec;
+#[path = "suites/traits_exec.rs"]
+mod traits_exec;
+#[path = "suites/traits_negative.rs"]
+mod traits_negative;
+#[path = "suites/type_demos_exec.rs"]
+mod type_demos_exec;
+#[path = "suites/types_exec.rs"]
+mod types_exec;
+#[path = "suites/utils_exec.rs"]
+mod utils_exec;
+#[path = "suites/warnings.rs"]
+mod warnings;