Let manual corrections outrank the model's own precedent

History rows now carry a source label: manual edits and merchant rules
are the user's decisions, ranked ahead of equally similar rows the
model classified itself and guaranteed slots in a full history window.
Without the distinction, precedent fed the model its own uncorrected
answers as majority evidence, so a correction never won against the
rows it was meant to fix. Both system prompts state that user entries
outrank ai entries. Alias write-back on manual merchant links and the
per-merchant usual category already learned locally; this closes the
loop for categories and tags.

internal/classification/ledger_test.go

@@ -2,6 +2,7 @@ package classification
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"reflect"
 	"strings"
@@ -156,3 +157,49 @@ func TestBICRedactionKeepsPayeeVocabulary(t *testing.T) {
 		}
 	}
 }
+
+// One manual correction must outrank any number of the model's own past
+// answers for the same payee: without source ranking, precedent feeds the
+// model its uncorrected output as majority evidence and corrections never
+// stick.
+func TestManualCorrectionsOutrankAIPrecedent(t *testing.T) {
+	d, _ := ledgerFixture()
+	groceries, events := "", ""
+	for _, c := range d.Categories {
+		if c.Name == "groceries" {
+			groceries = c.ID
+		}
+		if c.Name == "events" {
+			events = c.ID
+		}
+	}
+	add := func(id, date, category, source string) {
+		f := domain.Facts{ID: id, Source: "test", AccountID: "acct_kontist", BookingDate: date,
+			Amount: "-13.00", Currency: "EUR", Counterparty: "LVR Landesmuseum Bonn", Fingerprint: id}
+		d.Transactions = append(d.Transactions, domain.Transaction{Facts: f, Enrichment: domain.Enrichment{
+			Kind: "expense", CategoryID: category, TagIDs: []string{},
+			Classification: domain.Provenance{Source: source},
+		}})
+	}
+	// Many uncorrected AI answers, one older manual correction.
+	for i := range 30 {
+		add(fmt.Sprintf("tx_ai_%02d", i), "2026-08-20", groceries, "openrouter")
+	}
+	add("tx_corrected", "2026-08-01", events, "manual")
+	target := domain.Facts{ID: "tx_new", AccountID: "acct_kontist", BookingDate: "2026-08-30",
+		Amount: "-13.00", Currency: "EUR", Counterparty: "LVR Landesmuseum Bonn"}
+	rows := history(target, d, func(s string) string { return normalize(s) }, 20)
+	if len(rows) == 0 || rows[0].Source != "user" || rows[0].CategoryID != events {
+		t.Fatalf("manual correction did not lead precedent: %+v", rows[0])
+	}
+	// The correction keeps its slot even in a window the AI rows could fill.
+	users := 0
+	for _, row := range rows {
+		if row.Source == "user" {
+			users++
+		}
+	}
+	if users == 0 {
+		t.Fatal("correction crowded out of the history window")
+	}
+}