tty: coalesce queued input events into one frame; tracy zones behind -Dtracy

The tty shell rendered (core.render + full vaxis repaint + tree-sitter
re-highlight of the visible window) after EVERY event, so a wheel flick over a
highlighted file was 150 re-parses and 150 terminal repaints; the gui shell
drains the SDL queue before drawing and never had the issue. Now the tty loop
applies every queued input event, then renders once (batch cap 64; pty output
keeps a frame per chunk so progress paints and transient-state waits behave
exactly as before). Measured with tracy on a 2400-line .zig scroll script:
150 highlightFileRange calls at 1.85ms mean -> 4; render pipeline total
730ms -> 64ms; 364 frames -> 39. Snap suite 18/18.

Tracy: -Dtracy=<path-to-tracy-checkout> compiles TracyClient.cpp into the
binary and turns src/tracy.zig zones live (default off, all no-ops). Sampling,
callstacks, system tracing and the crash handler are disabled: tracy's symbol
worker SIGSEGVs on this binary's debug info and its crash handler then parks
every thread before the first frame. Capture: tracy-capture -o t.tracy; export:
tracy-csvexport t.tracy.

1 files changed, 50 insertions, 0 deletions

diff --git a/src/tracy.zig b/src/tracy.zig
new file mode 100644
index 00000000..3b0b8621
--- /dev/null
+++ b/src/tracy.zig
@@ -0,0 +1,50 @@
+//! Minimal Tracy client (the Zig compiler's pattern): `zone(@src(), "name")`
+//! ... `.end()`, plus `frameMark()`. Everything compiles to a no-op unless the
+//! build sets -Dtracy=<path-to-tracy-checkout>, which also compiles and links
+//! TracyClient.cpp. Capture with tracy-capture, inspect with tracy-csvexport.
+const std = @import("std");
+const builtin = @import("builtin");
+
+pub const enable = if (builtin.is_test) false else @import("pardes_config").enable_tracy;
+
+const SourceLocation = extern struct {
+    name: ?[*:0]const u8,
+    function: [*:0]const u8,
+    file: [*:0]const u8,
+    line: u32,
+    color: u32,
+};
+
+pub const Ctx = if (enable) extern struct {
+    id: u32,
+    active: i32,
+
+    pub inline fn end(c: @This()) void {
+        ___tracy_emit_zone_end(c);
+    }
+} else struct {
+    pub inline fn end(_: @This()) void {}
+};
+
+pub inline fn zone(comptime src: std.builtin.SourceLocation, comptime name: [:0]const u8) Ctx {
+    if (!enable) return .{};
+    const static = struct {
+        const loc: SourceLocation = .{
+            .name = name.ptr,
+            .function = src.fn_name.ptr,
+            .file = src.file.ptr,
+            .line = src.line,
+            .color = 0,
+        };
+    };
+    return ___tracy_emit_zone_begin(&static.loc, 1);
+}
+
+pub inline fn frameMark() void {
+    if (!enable) return;
+    ___tracy_emit_frame_mark(null);
+}
+
+extern fn ___tracy_emit_zone_begin(srcloc: *const SourceLocation, active: c_int) Ctx;
+extern fn ___tracy_emit_zone_end(ctx: Ctx) void;
+extern fn ___tracy_emit_frame_mark(name: ?[*:0]const u8) void;