fix(plugins): explain how to approve a process program installed after its grant (#1590)

A process: permission allowed while its program was missing has no pinned binary, so installing the program and restarting changes nothing. The error now says the program must be on PATH and that the permission has to be cleared and selected again in Settings › Plugins.

crates/ide-host/src/plugins/api.rs

@@ -306,8 +306,9 @@ impl PluginApi {
         // allowed, and installing it later approves nothing by itself.
         let pin = self.shared.pins.read().get(&(self.id().to_owned(), cap.clone())).cloned().ok_or_else(|| {
             HostError::Failed(format!(
-                "{cap}: `{program}` was not found when this permission was allowed; \
-                 install it, then allow {cap} again in Settings › Plugins"
+                "{cap}: `{program}` was not found on PATH when this permission was allowed. \
+                 Restarting doesn't approve a program installed later: once `{program}` is on PATH, \
+                 clear {cap} in Settings › Plugins and select it again"
             ))
         })?;
         pin.verify().map(Path::to_path_buf).map_err(|e| HostError::Denied(format!("{cap}: {e}")))
@@ -831,7 +832,8 @@ mod tests {
         // Allowed while the program was missing: say how to fix it rather than "not granted".
         let err = api.approved_program("lint").unwrap_err().to_string();
         assert!(
-            err.contains("was not found when this permission was allowed") && err.contains("allow process:lint again"),
+            err.contains("was not found on PATH when this permission was allowed")
+                && err.contains("clear process:lint in Settings › Plugins and select it again"),
             "{err}"
         );