zig build monkey: random snapshot scripts hunting panics

test/monkey.zig (Zig, as the project's tooling is): one random .snap per
seed, over bad-UTF-8, wide-glyph and long files: keys, leader bursts,
typing (an alphabet with no path characters), workspace words run by a
middle click (Newcol for narrow panes, Find and Grep for prompts, long
prompt text), presses, drags, wheel, hover, and resizes down to a cell.
pardes-snap runs it with --update; a panic is a record in the app's crash
file (in the script's fake home: seen even when the crash cut the script
short) or a `.zig:N:N: 0x` frame of the app's (not the harness's) in
its report or captured grid, and a hit keeps the script, captures and log
under --out (default /tmp/pardes-monkey). A seed always makes the same
script (tested), so --from=N replays one. Not a gate. README documents it
next to snap.

No Shader line: the tty has no post chain; the core fuzz in src/draw.zig
covers the compile-error notice at a gui's metrics.

80 seeds x 70 steps: no panic.

1 files changed, 19 insertions, 0 deletions

diff --git a/build/snap.zig b/build/snap.zig
index 6b3d2104..7aa06884 100644
--- a/build/snap.zig
+++ b/build/snap.zig
@@ -49,6 +49,25 @@ pub fn addTty(b: *std.Build, opts: struct {
     run_snap.has_side_effects = true;
     const snap_step = b.step("snap", "run the snapshot parity suite (-- --update regenerates goldens)");
     snap_step.dependOn(&run_snap.step);
+    // Random scripts through pardes-snap, hunting panics (test/monkey.zig):
+    // not a gate, it is slow and random over seeds; a seed replays.
+    const monkey = b.addExecutable(.{
+        .name = "pardes-monkey",
+        .root_module = b.createModule(.{
+            .target = opts.target,
+            .optimize = opts.optimize,
+            .root_source_file = b.path("test/monkey.zig"),
+            .link_libc = true,
+        }),
+    });
+    const run_monkey = b.addRunArtifact(monkey);
+    run_monkey.addArtifactArg(snap);
+    run_monkey.addArtifactArg(opts.exe);
+    if (b.args) |args| run_monkey.addArgs(args);
+    run_monkey.has_side_effects = true;
+    b.step("monkey", "random snapshot scripts hunting panics (-- <seeds> [steps] [--from=N] [--out=DIR])").dependOn(&run_monkey.step);
+    const monkey_tests = b.addTest(.{ .root_module = monkey.root_module });
+    b.step("monkey-test", "test the monkey's generator and panic detector").dependOn(&b.addRunArtifact(monkey_tests).step);
     const run_driver_test = b.addRunArtifact(snap);
     run_driver_test.addArg("--self-test");
     run_driver_test.has_side_effects = true;