Colour themes, defaulting to gruvbox dark

Every colour was a 256-colour ANSI index hardcoded in styles.go, so changing
the palette meant editing the styles themselves. This puts a semantic token set
between the two: styles name roles, a theme supplies the colours.

internal/theme holds the twelve tokens, the two built-ins (gruvbox-dark, the
new default, and gruvbox-light) and the loader for user themes in
~/.config/terdut-tui/themes/. A user file may 'extends:' a built-in and
override only what it cares about, and may shadow a built-in name to tweak it
in place. Unknown keys, malformed colours and incomplete themes are refused
with a message naming what went wrong.

Colours are truecolor hex now: lipgloss downsamples for 256- and 16-colour
terminals and honours NO_COLOR, so themes carry no fallbacks of their own.
An ANSI index is still accepted for anyone who would rather follow their
terminal's own palette.

The 21 package-level style vars become a Styles struct on the Model, which is
what rule 3 asked for all along; the four free functions in view.go take one as
their first argument. The embedded bubbles components are restyled from the
same tokens — otherwise a theme would leave a pink selected row and grey help
text behind. Note that the table's Cell style deliberately keeps no foreground:
bubbles renders cells before wrapping the row in Selected, so a colour there
cuts the selection highlight short.

internal/tui/view_test.go

@@ -7,6 +7,7 @@ import (
 	"time"
 
 	"git.ryuvia.com/niklas/terdut-tui/internal/api"
+	"git.ryuvia.com/niklas/terdut-tui/internal/theme"
 	tea "github.com/charmbracelet/bubbletea"
 )
 
@@ -16,6 +17,10 @@ var ansi = regexp.MustCompile(`\x1b\[[0-9;]*m`)
 
 func plain(s string) string { return ansi.ReplaceAllString(s, "") }
 
+// testStyles is the default theme, so assertions here run against what a user
+// with no 'theme:' key actually sees.
+func testStyles() Styles { return newStyles(theme.GruvboxDark) }
+
 func mustContain(t *testing.T, got string, wants ...string) {
 	t.Helper()
 	got = plain(got)
@@ -52,7 +57,7 @@ func TestIncidentDetail_RendersTheWholeStory(t *testing.T) {
 		{Type: api.EventNote, Username: "admin", Detail: "draining node-2", CreatedAt: now},
 	}
 
-	out := buildIncidentDetailContent(inc, timeline, -1, 110)
+	out := buildIncidentDetailContent(testStyles(), inc, timeline, -1, 110)
 	mustContain(t, out,
 		"DiskFull (namespace=prod)", "ACKNOWLEDGED", "CRITICAL",
 		"Assigned:", "admin",
@@ -72,7 +77,7 @@ func TestIncidentDetail_ShowsSnooze(t *testing.T) {
 	}
 	// The exact remaining time is humanUntil's business, not this test's — a few
 	// microseconds of elapsed clock turn "in 2h" into "in 1h 59m".
-	mustContain(t, buildIncidentDetailContent(inc, nil, -1, 110),
+	mustContain(t, buildIncidentDetailContent(testStyles(), inc, nil, -1, 110),
 		"TRIGGERED (snoozed)", "Snoozed:", "until", "in 1h")
 }
 
@@ -83,7 +88,7 @@ func TestIncidentDetail_HidesExpiredSnooze(t *testing.T) {
 		Title: "Noisy", Status: api.StatusTriggered,
 		TriggeredAt: time.Now(), SnoozedUntil: &past,
 	}
-	if strings.Contains(plain(buildIncidentDetailContent(inc, nil, -1, 110)), "Snoozed:") {
+	if strings.Contains(plain(buildIncidentDetailContent(testStyles(), inc, nil, -1, 110)), "Snoozed:") {
 		t.Error("an expired snooze should not be rendered")
 	}
 }
@@ -95,18 +100,18 @@ func TestIncidentDetail_ShowsResolutionSource(t *testing.T) {
 		Title: "Done", Status: api.StatusResolved, TriggeredAt: now.Add(-time.Hour),
 		ResolvedAt: &now, ResolutionSource: &source,
 	}
-	mustContain(t, buildIncidentDetailContent(inc, nil, -1, 110),
+	mustContain(t, buildIncidentDetailContent(testStyles(), inc, nil, -1, 110),
 		"RESOLVED", "Resolved:", "manual")
 }
 
 func TestIncidentDetail_UnassignedAndUnacknowledged(t *testing.T) {
 	inc := api.Incident{Title: "Fresh", Status: api.StatusTriggered, TriggeredAt: time.Now()}
-	mustContain(t, buildIncidentDetailContent(inc, nil, -1, 110), "nobody", "not acknowledged")
+	mustContain(t, buildIncidentDetailContent(testStyles(), inc, nil, -1, 110), "nobody", "not acknowledged")
 }
 
 func TestIncidentDetail_EmptyTimeline(t *testing.T) {
 	inc := api.Incident{Title: "Fresh", Status: api.StatusTriggered, TriggeredAt: time.Now()}
-	mustContain(t, buildIncidentDetailContent(inc, nil, -1, 110), "Nothing recorded yet")
+	mustContain(t, buildIncidentDetailContent(testStyles(), inc, nil, -1, 110), "Nothing recorded yet")
 }
 
 func TestIncidentDetail_MarksSelectedNote(t *testing.T) {
@@ -117,7 +122,7 @@ func TestIncidentDetail_MarksSelectedNote(t *testing.T) {
 	}
 	inc := api.Incident{Title: "X", Status: api.StatusTriggered, TriggeredAt: now}
 
-	out := plain(buildIncidentDetailContent(inc, timeline, 1, 110))
+	out := plain(buildIncidentDetailContent(testStyles(), inc, timeline, 1, 110))
 	for _, line := range strings.Split(out, "\n") {
 		if strings.Contains(line, "alice") && !strings.HasPrefix(line, "> ") {
 			t.Errorf("expected the selected note marked, got %q", line)
@@ -207,7 +212,7 @@ func TestIncidentDetail_RendersNotifications(t *testing.T) {
 			Detail: "reminder: ntfy returned 502", CreatedAt: now},
 	}
 
-	got := buildIncidentDetailContent(inc, timeline, -1, 120)
+	got := buildIncidentDetailContent(testStyles(), inc, timeline, -1, 120)
 	mustContain(t, got, "Notified niklas (triggered)", "Notification to niklas failed")
 }
 
@@ -230,7 +235,7 @@ func TestAlertDetail_SaysItIsReadOnlyAndLinksTheIncident(t *testing.T) {
 		Labels:      map[string]string{"instance": "node-1", "severity": "critical"},
 		Annotations: map[string]string{"summary": "disk 90%"},
 	}
-	mustContain(t, buildAlertDetailContent(alert, 110),
+	mustContain(t, buildAlertDetailContent(testStyles(), alert, 110),
 		"DiskFull", "FIRING", "Incident:", "#7", "press i to open it",
 		"instance", "node-1", "summary", "disk 90%",
 		"Alerts are read-only")
@@ -238,21 +243,21 @@ func TestAlertDetail_SaysItIsReadOnlyAndLinksTheIncident(t *testing.T) {
 
 func TestAlertDetail_NoIncident(t *testing.T) {
 	alert := api.Alert{ID: 3, Name: "Orphan", Status: "resolved", ReceivedAt: time.Now()}
-	mustContain(t, buildAlertDetailContent(alert, 110), "Incident:", "none")
+	mustContain(t, buildAlertDetailContent(testStyles(), alert, 110), "Incident:", "none")
 }
 
 func TestAlertDetail_ShowsResolutionSource(t *testing.T) {
 	source := "expiry"
 	alert := api.Alert{Name: "Gone", Status: "resolved", ReceivedAt: time.Now(),
 		ResolutionSource: &source}
-	mustContain(t, buildAlertDetailContent(alert, 110), "RESOLVED", "expiry")
+	mustContain(t, buildAlertDetailContent(testStyles(), alert, 110), "RESOLVED", "expiry")
 }
 
 // Null MTTA means nothing has been acknowledged, which is a different claim
 // from an instant response.
 func TestStats_RendersDashForMissingAverages(t *testing.T) {
 	stats := &api.IncidentStats{Total: 2, Triggered: 2}
-	out := buildStatsContent(stats, nil, nil, nil, 110)
+	out := buildStatsContent(testStyles(), stats, nil, nil, nil, 110)
 	mustContain(t, out, "Incident Response", "Mean time to acknowledge", "—",
 		"nothing has been acknowledged or resolved yet")
 }
@@ -260,12 +265,12 @@ func TestStats_RendersDashForMissingAverages(t *testing.T) {
 func TestStats_RendersAverages(t *testing.T) {
 	mtta, mttr := 150.0, 3600.0
 	stats := &api.IncidentStats{Total: 3, Resolved: 1, MTTASeconds: &mtta, MTTRSeconds: &mttr}
-	out := buildStatsContent(stats, []api.TopAlert{{Name: "DiskFull", Count: 4}}, nil, nil, 110)
+	out := buildStatsContent(testStyles(), stats, []api.TopAlert{{Name: "DiskFull", Count: 4}}, nil, nil, 110)
 	mustContain(t, out, "2m", "1h", "Top Alerts", "DiskFull")
 }
 
 func TestStats_HandlesNoIncidentData(t *testing.T) {
-	mustContain(t, buildStatsContent(nil, nil, nil, nil, 110), "Incident Response", "No data")
+	mustContain(t, buildStatsContent(testStyles(), nil, nil, nil, nil, 110), "Incident Response", "No data")
 }
 
 func TestView_TabsAndDashboardRender(t *testing.T) {
@@ -296,7 +301,7 @@ func TestView_EmptyStates(t *testing.T) {
 // The stats page renders inside the normal section chrome now, so it has to
 // survive the real path: a window size message sizes the viewport and fills it.
 func TestView_StatsSectionRendersInPlace(t *testing.T) {
-	m := NewModel(nil, "http://test", time.Minute)
+	m := NewModel(nil, "http://test", time.Minute, theme.GruvboxDark)
 	m.connected = true
 	m.incidentStats = &api.IncidentStats{Total: 3, Triggered: 1}
 	m.topAlerts = []api.TopAlert{{Name: "DiskFull", Count: 4}}
@@ -335,7 +340,7 @@ func TestFooter_IncidentDetailOffersResolveOnlyWhileOpen(t *testing.T) {
 }
 
 func TestView_ZeroWidthRendersNothing(t *testing.T) {
-	m := NewModel(nil, "http://test", time.Minute)
+	m := NewModel(nil, "http://test", time.Minute, theme.GruvboxDark)
 	if m.View() != "" {
 		t.Error("expected no output before the first window size message")
 	}