terminal: fix undefined memory in Tabstops code

src/font/Collection.zig

@@ -937,6 +937,9 @@ test init {
 }
 
 test "add full" {
+    // This test is way too slow to run under Valgrind, unfortunately.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     const testing = std.testing;
     const alloc = testing.allocator;
     const testFont = font.embedded.regular;

src/terminal/Tabstops.zig

@@ -129,6 +129,7 @@ pub fn resize(self: *Tabstops, alloc: Allocator, cols: usize) !void {
 
     // Note: we can probably try to realloc here but I'm not sure it matters.
     const new = try alloc.alloc(Unit, size);
+    @memset(new, 0);
     if (self.dynamic_stops.len > 0) {
         fastmem.copy(Unit, new, self.dynamic_stops);
         alloc.free(self.dynamic_stops);

src/terminal/page.zig

@@ -3042,6 +3042,10 @@ test "Page moveCells graphemes" {
 }
 
 test "Page verifyIntegrity graphemes good" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,
@@ -3063,6 +3067,10 @@ test "Page verifyIntegrity graphemes good" {
 }
 
 test "Page verifyIntegrity grapheme row not marked" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,
@@ -3090,6 +3098,10 @@ test "Page verifyIntegrity grapheme row not marked" {
 }
 
 test "Page verifyIntegrity styles good" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,
@@ -3122,6 +3134,10 @@ test "Page verifyIntegrity styles good" {
 }
 
 test "Page verifyIntegrity styles ref count mismatch" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,
@@ -3160,6 +3176,10 @@ test "Page verifyIntegrity styles ref count mismatch" {
 }
 
 test "Page verifyIntegrity zero rows" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,
@@ -3174,6 +3194,10 @@ test "Page verifyIntegrity zero rows" {
 }
 
 test "Page verifyIntegrity zero cols" {
+    // Too slow, and not really necessary because the integrity tests are
+    // only run in debug builds and unit tests verify they work well enough.
+    if (std.valgrind.runningOnValgrind() > 0) return error.SkipZigTest;
+
     var page = try Page.init(.{
         .cols = 10,
         .rows = 10,