fix(agent): gadfly round 1 — user-boundary scan, back-ref precedence, regex legibility

Two behavioral fixes from the review:

- modeSummary's backward scan now stops at the most recent user message.
  With the dwarf ratio rejecting the current turn's 1x-3x answer, the old
  unbounded scan could walk into WithHistory content and resurrect a stale
  answer to a DIFFERENT question — strictly worse than keeping the closer
  (opus, correctness). Other modes keep their historical unbounded scan.
- A terminal matching BOTH the ack shape and a back-reference is now
  classified back-ref: it carries no answer content, so the looser bar is
  the right one (opus, error-handling).

Plus the nits: summaryCloserRe assembled from named fragments, the leading
marker class gains '+' (parity with citationLabelRe), verb-first form takes
'all the', dwarf ratio hoisted into one named local, and the 151-vs-153
char/byte comment inaccuracy corrected.

Co-Authored-By: Claude Fable 5 <[email protected]>

agent/finalize_test.go

@@ -73,8 +73,9 @@ func TestIsCitationsOnly(t *testing.T) {
 }
 
 // b3cb9ee9Closer is the verbatim terminal turn from mort run b3cb9ee9: a
-// 2,089-char answer was front-loaded into the cite-call turn and this 151-char
-// compression was all that got delivered.
+// 2,089-char answer was front-loaded into the cite-call turn and this 153-byte
+// compression (151 runes — the em dash is 3 bytes, and byte length is what the
+// thresholds compare) was all that got delivered.
 const b3cb9ee9Closer = "Citations are logged. Short version: the bulk of that ~$64M was AIPAC and dark-money super PACs, not the party committees — and it still wasn't enough."
 
 func TestIsSummaryCloser(t *testing.T) {
@@ -91,6 +92,8 @@ func TestIsSummaryCloser(t *testing.T) {
 		{"done-prefix", "Done — citations logged.", true},
 		{"ack-then-tldr", "Sources have been recorded! TL;DR: the GPU was the bottleneck.", true},
 		{"references-noted", "References noted. In short: yes, it ships Tuesday.", true},
+		{"plus-list-marker", "+ Citations are logged.", true},
+		{"logged-all-the", "Logged all the citations.", true},
 
 		{"empty", "", false},
 		{"ack-continues-midsentence", "The citations are recorded in the court transcript, which shows the filing dates.", false},
@@ -141,6 +144,9 @@ func TestFinalOutput(t *testing.T) {
 	// A >=200-byte real answer that merely OPENS with a conversational word
 	// ("Sure,"). The preamble filter must NOT veto it (gadfly regression guard).
 	longConversationalAnswer := "Sure, here's the rundown: it currently sells for about $2,700 used on eBay, typically $2,400 to $2,900 depending on condition and bundle, with the sealed Founders Edition commanding the top of that range while used AIB cards go a bit lower."
+	// Matches BOTH the summary ack and backRefRe, within the 120-byte weak cap,
+	// and long enough (>~92 bytes) that longAnswer would fail the summary bar.
+	bothMatchCloser := "Citations are logged. As I mentioned above, the full detail on the money sources is in my earlier message."
 
 	tests := []struct {
 		name     string
@@ -347,6 +353,56 @@ func TestFinalOutput(t *testing.T) {
 			terminal: b3cb9ee9Closer,
 			want:     b3cb9ee9Closer,
 		},
+		{
+			// Gadfly (opus, correctness): the modeSummary scan must stop at the
+			// most recent user message. Here the current turn's answer sits in
+			// the 1x-3x band (rejected by the ratio) while a dwarfing answer to
+			// a DIFFERENT question sits in history — resurrecting it would be
+			// strictly worse than keeping the closer.
+			name: "summary closer never resurrects a stale answer across the user boundary",
+			msgs: []llm.Message{
+				llm.UserText("earlier, unrelated question?"),
+				asst(hugeAnswer),
+				llm.UserText("q?"),
+				asst(conciseAnswer, cite...),
+				llm.ToolResultsMessage(llm.ToolResult{ID: "c1", Name: "cite", Content: "ok"}),
+				asst(b3cb9ee9Closer),
+			},
+			terminal: b3cb9ee9Closer,
+			want:     b3cb9ee9Closer,
+		},
+		{
+			// The boundary must not break the legitimate multi-turn case: the
+			// dwarfing front-loaded answer in THIS turn's window is recovered
+			// even with history behind it.
+			name: "summary closer recovery still works with history present",
+			msgs: []llm.Message{
+				llm.UserText("earlier, unrelated question?"),
+				asst(longAnswer),
+				llm.UserText("q?"),
+				asst(hugeAnswer, cite...),
+				llm.ToolResultsMessage(llm.ToolResult{ID: "c1", Name: "cite", Content: "ok"}),
+				asst(b3cb9ee9Closer),
+			},
+			terminal: b3cb9ee9Closer,
+			want:     hugeAnswer,
+		},
+		{
+			// Gadfly (opus, error-handling): a closer matching BOTH the ack
+			// shape and a back-reference carries no answer content, so the
+			// back-ref test must win and the ordinary recovery bar apply —
+			// under the summary bar this ~106-byte terminal would demand a
+			// ~318-byte prior and wrongly keep the closer over longAnswer.
+			name: "back-reference wins over the summary ack when both match",
+			msgs: []llm.Message{
+				llm.UserText("q?"),
+				asst(longAnswer, cite...),
+				llm.ToolResultsMessage(llm.ToolResult{ID: "c1", Name: "cite", Content: "ok"}),
+				asst(bothMatchCloser),
+			},
+			terminal: bothMatchCloser,
+			want:     longAnswer,
+		},
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {