docs: Phase 190-impl-D complete - NumberAccumulation PHI wiring fixed

- Fixed ValueId collision between body-local and carrier params
- Added ExitLine contract verifier (debug assertions)
- Updated test files to use Main box
- E2E verified: atoi→12, parse_number→123

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/tests/phase190_parse_number_impl.hako

@@ -5,8 +5,8 @@
 // Expected: i=1,2,3 → num = 0*10+1 = 1 → 1*10+2 = 12 → 12*10+3 = 123
 // Result should be 123
 
-static box ParseNumberImpl {
-    method main() {
+static box Main {
+    main() {
         local num
         num = 0
         local i
@@ -19,6 +19,6 @@ static box ParseNumberImpl {
             i = i + 1
         }
         print(num)
-        return num
+        return 0
     }
 }