feat(offscreen): read recent proposals into the brief; prompt follows up

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/ai/proposer.go

@@ -39,6 +39,7 @@ Respond with ONLY a JSON object, no prose and no code fences, exactly this shape
 Rules:
 - next_action: a single concrete off-screen action, doable now.
 - rationale: one short sentence naming the goal or value it serves.
+- If the brief lists recently proposed actions, do not simply repeat them; if a recent one was dismissed or not done and still fits, follow up on it instead of inventing something new.
 
 ## Brief
 ` + brief

internal/ai/proposer_test.go

@@ -41,3 +41,10 @@ func TestProposePromptIncludesBrief(t *testing.T) {
 		t.Fatalf("prompt should embed the brief, got: %s", fb.gotPrompt)
 	}
 }
+
+func TestProposePromptHasFollowUpRule(t *testing.T) {
+	p := buildProposePrompt("brief")
+	if !strings.Contains(p, "do not simply repeat") {
+		t.Fatalf("prompt missing follow-up rule:\n%s", p)
+	}
+}