fix: align bench/build diagnostic assertions with actionable contract (#7975)

Several library tests asserted obsolete diagnostic wording and blocked the
Rust test gate, even though the exercised behavior already returns the
intended, more actionable diagnostics.

- Duplicate bench scenario tests expected the old validate.rs phrasing
  ("duplicate bench scenario id `x`" / "workload paths relative to the
  bench root") and `details.id == "<scenario>"`. The current
  `resolve_duplicate_scenario_ids` path emits the structured
  `duplicate_scenario_id` diagnostic naming both discovered source paths
  with `--path` / `--rig` remediation, and carries the diagnostic code in
  `details.id`. Assertions now validate that contract (covers the two
  listed tests plus selected_parse_still_rejects_selected_duplicate...,
  which had the same stale wording).

- resolve_build_command_guides_unconfigured_components and
  extension_guidance_hints_point_to_supported_paths both expect a
  `scripts.build` component-owned-command hint that the guidance helper no
  longer emitted. Restore the `scripts.<capability>` hint so the
  unconfigured-component diagnostic actually points at the escape hatch
  both tests document.

All bench parsing (45), extension (29), and the named build tests pass.

Author: chubes4

src/core/extension/bench/parsing/mod.rs

@@ -1379,17 +1379,33 @@ mod tests {
             .and_then(|v| v.as_str())
             .unwrap_or("");
 
+        // The duplicate is surfaced by `resolve_duplicate_scenario_ids`, which
+        // emits the structured `duplicate_scenario_id` diagnostic naming the
+        // conflicting id, both discovered source paths, and the actionable
+        // `--path` / `--rig` remediation.
         assert!(
-            problem.contains("duplicate bench scenario id `heavy`"),
+            problem.contains("duplicate bench scenario id(s) discovered"),
             "expected duplicate-id problem, got: {}",
             problem
         );
+        assert!(
+            problem.contains("`heavy`"),
+            "problem should name the id: {problem}"
+        );
         assert!(problem.contains("tests/bench/reads/heavy.php"));
         assert!(problem.contains("tests/bench/writes/heavy.php"));
-        assert!(problem.contains("workload paths relative to the bench root"));
+        assert!(
+            problem.contains("homeboy bench --path <workspace>"),
+            "problem should offer the --path remediation: {problem}"
+        );
+        assert!(
+            problem.contains("--rig <id>"),
+            "problem should offer the --rig remediation: {problem}"
+        );
+        // `id` carries the diagnostic code, not the scenario id.
         assert_eq!(
             err.details.get("id").and_then(|v| v.as_str()),
-            Some("heavy")
+            Some("duplicate_scenario_id")
         );
     }
 
@@ -1459,7 +1475,14 @@ mod tests {
             .and_then(|v| v.as_str())
             .unwrap_or("");
 
-        assert!(problem.contains("duplicate bench scenario id `target`"));
+        assert!(
+            problem.contains("duplicate bench scenario id(s) discovered"),
+            "expected duplicate-id problem, got: {problem}"
+        );
+        assert!(
+            problem.contains("`target`"),
+            "problem should name the id: {problem}"
+        );
     }
 
     #[test]

src/core/extension/capability.rs

@@ -232,8 +232,23 @@ pub(crate) fn extension_guidance_hints(
         ),
     };
 
+    // Point at the component-owned escape hatch too: a component can supply its
+    // own command via a `scripts.<capability>` entry without linking an
+    // extension at all. Named after the capability so the hint is actionable
+    // (e.g. `scripts.build`) and independently regression-covered.
+    let scripts_hint = match capability {
+        Some(capability) => format!(
+            "Use `scripts.{}` for component-owned {} commands (no extension required): set it in the component config.",
+            capability.label().to_lowercase(),
+            capability.label().to_lowercase()
+        ),
+        None => "Use `scripts.<command>` for component-owned commands (no extension required): set it in the component config."
+            .to_string(),
+    };
+
     vec![
         link_hint,
+        scripts_hint,
         "List installed extensions: homeboy extension list".to_string(),
         format!(
             "Component config lives at ~/.config/homeboy/components/{}.json or in a portable homeboy.json discovered from the component path.",