Fix the console: std.time.milliTimestamp does not exist, and zig build test could not see it

`zig build interact` did not compile. The mouse coalescer dated its held report with
`std.time.milliTimestamp`, and this Zig's `std.time` has constants and `epoch` and no clock
at all: the repo's own idiom is `std.Io.Timestamp`, already wrapped as `serial.Port.nowMs`,
which is what the three call sites now use.

The reason it survived every check I ran is worth writing down, because the same hole will
swallow the next one. `zig build test` compiles `tools/console.zig` as a test module, and
Zig only analyses what is REACHABLE: no test calls `attach`, so the loop containing the bad
call was never looked at. Seven passing MouseFilter tests and a green `zig build test` said
nothing whatsoever about whether the file compiles as part of an executable. Nor does plain
`zig build` - p4-console is not in the default install step - so the only thing that would
have caught it is building or running the named step, which is also the documented way to
use this repo: `zig build interact -Dpardes`.

Verified the way it should have been the first time: `zig build interact -Dpardes
-Dcpu-mhz=360` with piped stdin flashes, attaches, takes the keystrokes and detaches at
EOF. Also compiled every step's artifacts - elf, console, bench - and re-ran the matrix
that matters for the editor side: default, Debug, ReleaseFast, ReleaseSafe, ReleaseSmall,
and -Dplatform=p4 at Debug and ReleaseSmall, plus -Dp4-cols/-Dp4-rows at 40x12 and 80x24.

Note for anyone reading a failing `zig build console` or `bench`: those RUN their tool, so
they fail with DeviceBusy when something else is attached to the port. That is not a build
error, and it is how this one hid in plain sight in the middle of the output.

1 files changed, 3 insertions, 3 deletions

diff --git a/tools/console.zig b/tools/console.zig
index 4b13513..39a829b 100644
--- a/tools/console.zig
+++ b/tools/console.zig
@@ -336,7 +336,7 @@ pub fn attach(port_path: []const u8, baud: serial.Baud, opts: Options) !void {
         // A bounded wait, and shorter while a motion report is being held: the hold has to end on
         // time even when the human has stopped moving the mouse and nothing else is arriving.
         const wait: i32 = if (held_at) |at| blk: {
-            const left = coalesce_ms - (std.time.milliTimestamp() - at);
+            const left = coalesce_ms - (port.nowMs() - at);
             break :blk if (left <= 0) 0 else @intCast(left);
         } else 200;
         const ready = posix.poll(&pfd, wait) catch continue;
@@ -385,9 +385,9 @@ pub fn attach(port_path: []const u8, baud: serial.Baud, opts: Options) !void {
         // The coalescing window. A held motion report goes out when the interval has elapsed, which
         // is what turns a drag into a bounded stream of positions rather than one per cell crossed.
         if (mouse.pending()) {
-            const at = held_at orelse std.time.milliTimestamp();
+            const at = held_at orelse port.nowMs();
             held_at = at;
-            if (std.time.milliTimestamp() - at >= coalesce_ms) {
+            if (port.nowMs() - at >= coalesce_ms) {
                 const send = mouse.flushHeld(&to_board);
                 if (send > 0) port.write(to_board[0..send]) catch {};
                 held_at = null;