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, 3 insertions, 0 deletions

diff --git a/src/syntax.zig b/src/syntax.zig
index a9914fd7..0d2fa291 100644
--- a/src/syntax.zig
+++ b/src/syntax.zig
@@ -4,6 +4,7 @@
 //! compiles queries at startup; `full` adds ~23 languages lazily on first use.
 const std = @import("std");
 const config = @import("pardes_config");
+const tracy = @import("tracy.zig");
 
 pub const enabled = config.syntax_highlighting;
 const minimal_grammars = config.syntax_minimal_grammars;
@@ -140,6 +141,8 @@ pub fn highlightFile(gpa: std.mem.Allocator, path: []const u8, content: []const
 
 /// One Syn byte per content byte in [start, end). Caller frees.
 pub fn highlightFileRange(gpa: std.mem.Allocator, path: []const u8, content: []const u8, start_byte_raw: usize, end_byte_raw: usize) ![]u8 {
+    const tz = tracy.zone(@src(), "highlightFileRange");
+    defer tz.end();
     if (!enabled) return &.{};
     const ext = std.fs.path.extension(path);
     const selected = (forExt(ext) catch return &.{}) orelse return &.{};