A component with nothing built is not current with the checkout

`freshness` compared two commits and never asked whether there was an
output at all, so a component built once and then cleaned reported the
commit it was last built from and read as `current`: the card said
nothing, filed it under "up to date", and offered Rebuild for a build
that did not exist. Found on test-projects/two-clients, whose tablet
component had a recorded builtFrom and no APK under it.

The staleness rules already knew -- `component_is_stale` has asked
`find_apks` under the component's own directory since per-component
discovery landed -- so the two readers of "is this build current"
disagreed, which is the shape worth removing rather than the one wrong
answer. Both now go through `nothing_built`.

Only for an Apk, since a Server has none to find, and only for a
component this server builds, since with no command there is nothing to
press and saying it would be a nag about a project built by hand.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/src/build_state.rs

@@ -592,6 +592,18 @@ impl BuildState {
         if component.built_in_another_mode() {
             return Freshness::Behind;
         }
+        // Nothing built at all, which no commit can express either: the
+        // comparison below is between two commits, so a component whose
+        // output was removed -- or never produced on this machine --
+        // reports the commit it was last built from and reads as current,
+        // with the card saying nothing and its button offering to build it
+        // *again*. Asked here as well as in `component_is_stale` through
+        // one function, because the two answering it differently is what
+        // produced that: the staleness rules knew there was no build and
+        // the card did not.
+        if self.nothing_built(component) {
+            return Freshness::Behind;
+        }
         let built = self
             .inner
             .lock()
@@ -614,6 +626,38 @@ impl BuildState {
         }
     }
 
+    /// Whether this component has no build output at all.
+    ///
+    /// The state a commit cannot express, which is why both readers of
+    /// "is this build current" have to ask it separately from comparing
+    /// commits: `component_is_stale`, so a first build can be triggered,
+    /// and `freshness`, so the card does not call a component with nothing
+    /// on disk up to date. They asked it in one place only for a while,
+    /// and a component whose APK had been removed after a build read as
+    /// `current` on the card while the staleness rules knew better --
+    /// nothing looked broken, which is what makes that shape expensive.
+    ///
+    /// Scoped to *this component's own* directory, not the project root: a
+    /// project producing two APKs has one component's output sitting under
+    /// the root-anchored patterns too (an inner
+    /// `*/build/outputs/apk/*/*.apk` matches a one-level subdirectory
+    /// regardless of which component it belongs to), which made the whole
+    /// project read as "something is built here" the moment either
+    /// component had ever been built -- masking that the *other*
+    /// component, never built, had nothing to trigger it.
+    ///
+    /// Only asked of an `Apk`: a `Server` never has one to find under its
+    /// own directory by definition, so the same question asked of it would
+    /// report every server "never built" for ever. And only of a component
+    /// this server builds: with no command there is nothing to press, so
+    /// saying it out loud would be a nag about a project somebody builds
+    /// by hand.
+    fn nothing_built(&self, component: &Component) -> bool {
+        !component.build().is_empty()
+            && matches!(component, Component::Apk { .. })
+            && crate::discover::find_apks(&component.dir(&self.project_path)).is_empty()
+    }
+
     fn component_is_stale(
         &self,
         component: &Component,
@@ -638,23 +682,7 @@ impl BuildState {
         // never been built reports not-stale under it and would leave the
         // first build impossible to trigger -- which a project can be
         // added before having done.
-        //
-        // Scoped to *this component's own* directory, not the project
-        // root: a project producing two APKs has one component's output
-        // sitting under the root-anchored patterns too (an inner
-        // `*/build/outputs/apk/*/*.apk` matches a one-level subdirectory
-        // regardless of which component it belongs to), which made the
-        // whole project read as "something is built here" the moment
-        // either component had ever been built -- masking that the
-        // *other* component, never built, had nothing to trigger it.
-        //
-        // Only asked of an `Apk`: a `Server` never has one to find under
-        // its own directory by definition, so the same question asked of
-        // it would report every server "never built" for ever, which is
-        // exactly the false staleness this check exists to rule out.
-        if matches!(component, Component::Apk { .. })
-            && crate::discover::find_apks(&component.dir(&self.project_path)).is_empty()
-        {
+        if self.nothing_built(component) {
             return true;
         }
         // Behind the checkout: this component was built from a commit
@@ -2081,6 +2109,48 @@ mod tests {
         }
     }
 
+    /// A component with nothing built is not "current with the checkout",
+    /// however still the commits are.
+    ///
+    /// Found on a two-APK test project whose second component had been
+    /// built once and had its output removed since: the card said nothing,
+    /// filed it under "up to date", and offered *Rebuild* for a component
+    /// with no build to re-do. Every commit involved was equal, which is
+    /// all `freshness` used to look at.
+    #[test]
+    fn a_component_with_no_output_is_not_reported_as_current() {
+        let dir = tempfile::tempdir().expect("tempdir");
+        let root = dir.path();
+        let components = two_component_checkout(root);
+        let head = crate::git::subtree_head(root, &[PathBuf::from("app")]).expect("a commit");
+        let state = state_for(root, components);
+        // Built here, at the commit that is still checked out: as current
+        // as a comparison of commits can make it.
+        state
+            .inner
+            .lock()
+            .unwrap()
+            .built_from
+            .insert("app".to_string(), head);
+        let app = state
+            .components
+            .iter()
+            .find(|component| component.name() == "app")
+            .expect("the app component");
+        assert_eq!(state.freshness(app, false), Freshness::Current);
+
+        std::fs::remove_file(root.join("app/build/outputs/apk/debug/a.apk")).expect("rm");
+        assert_eq!(
+            state.freshness(app, false),
+            Freshness::Behind,
+            "the commits still match, and there is nothing built to match them",
+        );
+        assert!(
+            stale(&state, "app"),
+            "and the two readers of this agree, which is the point of asking it once",
+        );
+    }
+
     /// The shape of bug a unit test that only calls `component_is_stale`
     /// cannot see: `status()` and `trigger_if_needed` hold the lock that
     /// the staleness check also wants. Taking it twice on one thread is a