test: add 116 integration tests closing dispatch-layer blind spot

Cargo.toml

@@ -48,6 +48,9 @@ path = "src/main.rs"
 [dev-dependencies]
 stats = { path = "stats" }
 ignore = "0.4"
+assert_cmd = "2"
+predicates = "3"
+proptest = "1"
 
 [[bench]]
 name = "benchmarks"

perf.toml

@@ -82,5 +82,14 @@ files = [
     "xtask/src/bench.rs",
     "xtask/src/find_entry.rs",
     "tests/perf_registry.rs",
+    "tests/common/mod.rs",
+    "tests/cli.rs",
+    "tests/session_reports.rs",
+    "tests/json_roundtrip.rs",
+    "tests/git_refs.rs",
+    "tests/cache_safety.rs",
+    "tests/negative_cases.rs",
+    "tests/property.rs",
+    "tests/report_battery.rs",
 ]
 benchmarks = []

src/error.rs

@@ -38,6 +38,13 @@ pub enum Error {
     InvalidTopValue(&'static str, i32),
     /// Readline/REPL initialization failed.
     Readline(String),
+    /// --max-weight threshold exceeded.
+    MaxWeightExceeded {
+        kind: &'static str,
+        weight: u64,
+        module_count: usize,
+        threshold: u64,
+    },
 }
 
 impl Error {
@@ -113,6 +120,20 @@ impl std::fmt::Display for Error {
                 write!(f, "invalid value {n} for {flag}: must be -1 (all) or 0+")
             }
             Self::Readline(msg) => write!(f, "readline: {msg}"),
+            Self::MaxWeightExceeded {
+                kind,
+                weight,
+                module_count,
+                threshold,
+            } => {
+                let plural = if *module_count == 1 { "" } else { "s" };
+                write!(
+                    f,
+                    "{kind} transitive weight {} ({module_count} module{plural}) exceeds --max-weight threshold {}",
+                    crate::report::format_size(*weight),
+                    crate::report::format_size(*threshold),
+                )
+            }
         }
     }
 }