feat: triple-toggle CPU display mode via 1 key; add tooltip, font, hit-test

CPU display now cycles through three states with each press of 1:
  0 = CPUModeAverage  – aggregate bar only (default)
  1 = CPUModeCores    – individual core bars + aggregate
  2 = CPUModeOff      – all CPU bars hidden

Config file stores cpumode=N (integer); old showcores=0/1 is read for
backward compatibility. CLI flag --showcores replaced by --cpumode.

Other improvements landed in this commit:
- internal/display: add font.go (text rendering), hittest.go (bar hit
  testing), tooltip.go (mouse-over tooltip), tooltip_test.go
- internal/display: mouse tracking and drawOverlay hook in display.go
- internal/display: update build tags to //go:build form
- internal/collector: embed remote script via script_embed.go /
  scriptdata/loadbars-remote.sh
- internal/collector: CPULine.Total() changed to value receiver
- internal/collector: table test improvements (name field, t.Run)
- internal/constants: BytesPerSec consts promoted from var to const
- Magefile.go: fix error formatting and install path

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

2 files changed, 18 insertions, 11 deletions

diff --git a/internal/config/config.go b/internal/config/config.go
index ba7886e..90b8192 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -26,7 +26,7 @@ type Config struct {
 	NetLink    string
 	ShowAvgLine    bool
 	ShowIOAvgLine  bool
-	ShowCores      bool
+	CPUMode        int // constants.CPUModeAverage / CPUModeCores / CPUModeOff
 	ShowMem        bool
 	ShowNet        bool
 	ShowSeparators bool
@@ -46,7 +46,7 @@ func Default() Config {
 		MaxWidth:   1900,
 		NetAverage: 15,
 		NetLink:    "gbit",
-		ShowCores:     false,
+		CPUMode:       constants.CPUModeAverage, // start with aggregate bar only
 		ShowMem:       false,
 		ShowNet:       false,
 		MaxBarsPerRow: 0,
@@ -108,7 +108,7 @@ func (c *Config) parseReader(f *os.File) error {
 	validKeys := map[string]bool{
 		"title": true, "barwidth": true, "cpuaverage": true, "extended": true,
 		"hasagent": true, "height": true, "maxwidth": true, "netaverage": true,
-		"netlink": true, "showcores": true, "showmem": true,
+		"netlink": true, "cpumode": true, "showcores": true, "showmem": true,
 		"showavgline": true, "showioavgline": true, "shownet": true, "showseparators": true,
 		"maxbarsperrow": true, "sshopts": true, "cluster": true,
 	}
@@ -169,8 +169,18 @@ func (c *Config) set(key, val string) {
 		c.ShowAvgLine = parseBool(val)
 	case "showioavgline":
 		c.ShowIOAvgLine = parseBool(val)
+	case "cpumode":
+		// 0=average, 1=cores, 2=off — clamp to valid range
+		if n, err := strconv.Atoi(val); err == nil && n >= 0 && n < constants.CPUModeCount {
+			c.CPUMode = n
+		}
 	case "showcores":
-		c.ShowCores = parseBool(val)
+		// Backward-compatible: old boolean showcores maps to CPUMode
+		if parseBool(val) {
+			c.CPUMode = constants.CPUModeCores
+		} else {
+			c.CPUMode = constants.CPUModeAverage
+		}
 	case "showmem":
 		c.ShowMem = parseBool(val)
 	case "shownet":
@@ -209,7 +219,7 @@ func (c *Config) writeTo(f *os.File) error {
 	writeStr("netlink", c.NetLink)
 	writeBool("showavgline", c.ShowAvgLine)
 	writeBool("showioavgline", c.ShowIOAvgLine)
-	writeBool("showcores", c.ShowCores)
+	writeInt("cpumode", c.CPUMode)
 	writeBool("showmem", c.ShowMem)
 	writeBool("shownet", c.ShowNet)
 	writeBool("showseparators", c.ShowSeparators)
diff --git a/internal/config/config_test.go b/internal/config/config_test.go
index 630fa47..7b0bb37 100644
--- a/internal/config/config_test.go
+++ b/internal/config/config_test.go
@@ -25,9 +25,6 @@ func TestConfig_parseReader(t *testing.T) {
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			c := Default()
-			f, _ := os.Open(os.DevNull)
-			defer f.Close()
-			// Use a temp file with the content since parseReader takes *os.File
 			dir := t.TempDir()
 			path := filepath.Join(dir, "rc")
 			if err := os.WriteFile(path, []byte(tt.input), 0600); err != nil {
@@ -54,7 +51,7 @@ func TestConfig_parseReader(t *testing.T) {
 func TestConfig_writeTo(t *testing.T) {
 	c := Default()
 	c.BarWidth = 25
-	c.ShowCores = true
+	c.CPUMode = 1 // CPUModeCores
 	dir := t.TempDir()
 	path := filepath.Join(dir, "out")
 	f, err := os.Create(path)
@@ -73,8 +70,8 @@ func TestConfig_writeTo(t *testing.T) {
 	if !bytes.Contains(data, []byte("barwidth=25")) {
 		t.Errorf("expected barwidth=25 in %s", data)
 	}
-	if !bytes.Contains(data, []byte("showcores=1")) {
-		t.Errorf("expected showcores=1 in %s", data)
+	if !bytes.Contains(data, []byte("cpumode=1")) {
+		t.Errorf("expected cpumode=1 in %s", data)
 	}
 }