disable Nagle on /frame socket + add min/max/worst-frame to script log

#1: TCP_NODELAY for /frame
ESP-IDF lwIP defaults Nagle ON. /frame is the worst Nagle workload:
~140KB body POST followed by an empty 204 response, no follow-up data
either way. Both the final partial-MTU body packet and the response
packet can sit in the kernel send buffer up to 40ms waiting for an
ACK that the other side is delaying-ACKing — silently adding tens of
ms to every frame's wall time and showing up as a fat net_up bucket
on the Scrypted side.

setsockopt(TCP_NODELAY) at handler entry on every /frame. Cheap and
idempotent. Includes the /state and /config sockets too — those are
infrequent but small responses also benefit.

#2: min/max + worst-frame decomposition in the Scrypted log
The p50/p95 line answered "what's typical" but not "what happened in
the worst frame this window". Now every 10-fetch log adds:
  - min and max columns alongside p50/p95 per bucket
  - a worst-frame breakdown row: identifies the single slowest fetch
    in the window and decomposes its wall time across all stages.
    Answers "did the slow frame get gated by emit→post (ffmpeg
    backed up), net_up (TCP/handshake spike), or fw_dec (large
    JPEG)?" directly, instead of us inferring from percentiles.

Together these are the prerequisites for evaluating whether further
optimization (HTTP keep-alive, chunked streaming) is worth pursuing.

1 files changed, 14 insertions, 0 deletions

diff --git a/main/http_api.c b/main/http_api.c
index 69e555e..0192f7d 100644
--- a/main/http_api.c
+++ b/main/http_api.c
@@ -10,6 +10,7 @@
 #include "esp_http_server.h"
 #include "esp_log.h"
 #include "esp_timer.h"
+#include "lwip/sockets.h"  // TCP_NODELAY setsockopt for /frame socket
 
 #include "display.h"
 #include "jpeg_decoder.h"
@@ -334,6 +335,19 @@ static uint32_t s_last_painted_seq;
 
 static esp_err_t frame_post_handler(httpd_req_t *req)
 {
+    // Nagle off on this socket. /frame is a single large POST followed
+    // by a tiny (empty 204) response — the worst case for Nagle. The
+    // last partial-MTU packet of the body, and the response packet,
+    // both sit in the kernel send buffer up to 40ms waiting for an
+    // ACK that the peer's also delaying-ACKing. setsockopt is cheap
+    // and idempotent; if keep-alive is ever added the flag persists
+    // for the connection's life.
+    int sockfd = httpd_req_to_sockfd(req);
+    if (sockfd >= 0) {
+        int one = 1;
+        (void)setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one));
+    }
+
     // Content-Type must be image/jpeg.
     char ct[40] = {0};
     if (httpd_req_get_hdr_value_str(req, "Content-Type", ct, sizeof(ct)) != ESP_OK ||