fix(card): show 7 *named* languages + Other, not 6 + Other (#19)

With topN=7 the previous collapseOther kept only the first 6 entries
and added "Other" as the 7th row. A user expecting to see 7 actual
languages in the legend saw six named languages plus "Other" — the
exact complaint just raised about the profile repo's donut.

Flip the semantic: the "top N" slots are reserved for real languages,
and "Other" is an extra row when (and only when) there's a non-zero
tail past the Nth entry. Topologically that means up to 8 legend
rows — still fits the card frame (row 8 text baseline at y=195, card
height 200).

- TestDonutTopSevenPlusOther pins the new contract with a 9-language
  input.
- adversarialProfile in TestCardsFitFrame bumped to 9 languages so
  the stress test exercises the 8-row legend geometry.
- design-guidelines: the donut row re-reads "Up to 7 named languages,
  plus an 'Other' row when the tail is non-zero (8 rows max)".

docs/design-guidelines.md

@@ -50,7 +50,7 @@ Cap rows at what fits: up to 7 rows per card. Stats splits commits into lifetime
 | Donut centre | `(250, 110)` |
 | Outer radius | 55 |
 | Inner radius | 30 |
-| Top-N entries shown | 7 (overflow collapses into "Other") |
+| Top-N entries shown | Up to 7 named languages, plus an "Other" row when the tail is non-zero (8 rows max) |
 | Slice stroke | `theme.Background`, 1.5 px (gap between slices) |
 | Legend origin | `(20, 55)` |
 | Legend row height | 20 px |

internal/card/card_test.go

@@ -141,6 +141,37 @@ func TestDonutEmpty(t *testing.T) {
 	}
 }
 
+// TestDonutTopSevenPlusOther confirms the "7 named + Other" contract: when
+// the input has more than 7 languages, the legend shows all 7 real entries
+// followed by a single "Other" bucket. Regression guard against anyone
+// sliding topN back to "N-1 real + Other" packing.
+func TestDonutTopSevenPlusOther(t *testing.T) {
+	th, _ := theme.Lookup("dracula")
+	stats := []github.LangStat{
+		{Name: "Go", Color: "#00ADD8", Value: 100},
+		{Name: "TypeScript", Color: "#3178c6", Value: 90},
+		{Name: "Python", Color: "#3572A5", Value: 80},
+		{Name: "Rust", Color: "#dea584", Value: 70},
+		{Name: "JavaScript", Color: "#f1e05a", Value: 60},
+		{Name: "HTML", Color: "#e34c26", Value: 50},
+		{Name: "Shell", Color: "#89e051", Value: 40},
+		{Name: "Kotlin", Color: "#A97BFF", Value: 30},
+		{Name: "Java", Color: "#b07219", Value: 20},
+	}
+	svg := string(renderDonutCard("Test", stats, th))
+	for _, want := range []string{"Go", "TypeScript", "Python", "Rust", "JavaScript", "HTML", "Shell", "Other"} {
+		if !strings.Contains(svg, ">"+want+" ") {
+			t.Errorf("expected legend row for %q; not found in:\n%s", want, svg)
+		}
+	}
+	// Kotlin + Java spill into Other (they must NOT appear as named rows).
+	for _, dropped := range []string{">Kotlin ", ">Java "} {
+		if strings.Contains(svg, dropped) {
+			t.Errorf("expected %q to be collapsed into Other, but it renders:\n%s", dropped, svg)
+		}
+	}
+}
+
 func TestFormatInt(t *testing.T) {
 	cases := map[int]string{
 		0:       "0",
@@ -356,12 +387,19 @@ func adversarialProfile() *github.Profile {
 		TotalContributedTo:         777,
 		TotalContributionsLastYear: 200_000,
 		CreatedAt:                  time.Date(2008, 1, 1, 0, 0, 0, 0, time.UTC),
+		// Nine languages so the donut's "top 7 + Other" layout renders all
+		// eight legend rows — catches any regression that breaks the tall
+		// legend geometry at y≈195.
 		ReposByLanguage: []github.LangStat{
 			{Name: "JavaScript", Color: "#f1e05a", Value: 1234},
 			{Name: "TypeScript", Color: "#3178c6", Value: 999},
 			{Name: "Go", Color: "#00ADD8", Value: 500},
 			{Name: "Rust", Color: "#dea584", Value: 321},
 			{Name: "Python", Color: "#3572A5", Value: 200},
+			{Name: "HTML", Color: "#e34c26", Value: 180},
+			{Name: "Shell", Color: "#89e051", Value: 120},
+			{Name: "Kotlin", Color: "#A97BFF", Value: 60},
+			{Name: "Java", Color: "#b07219", Value: 30},
 		},
 		CommitsByLanguage: []github.LangStat{
 			{Name: "JavaScript", Color: "#f1e05a", Value: 1_000_000},

internal/card/donut_chart.go

@@ -99,19 +99,23 @@ func polar(cx, cy float64, r, angle float64) (float64, float64) {
 	return cx + r*math.Cos(angle), cy + r*math.Sin(angle)
 }
 
-// collapseOther returns the top (n-1) slices plus an "Other" row summing the
-// rest. When the slice fits, it's returned as-is.
+// collapseOther returns the top n named entries, optionally followed by an
+// "Other" row summing everything past that. "Top N" means N actual languages
+// — the Other row is a bonus when there's a non-zero tail, not one of the N.
+// When the input fits in N entries the caller gets the slice back as-is.
 func collapseOther(in []github.LangStat, n int) []github.LangStat {
 	if len(in) <= n {
 		return in
 	}
-	out := make([]github.LangStat, 0, n)
-	out = append(out, in[:n-1]...)
+	out := make([]github.LangStat, 0, n+1)
+	out = append(out, in[:n]...)
 	var rest int64
-	for _, s := range in[n-1:] {
+	for _, s := range in[n:] {
 		rest += s.Value
 	}
-	out = append(out, github.LangStat{Name: "Other", Value: rest})
+	if rest > 0 {
+		out = append(out, github.LangStat{Name: "Other", Value: rest})
+	}
 	return out
 }