Trim task stacks and buffers by measurement: +15 KB with IRC up

Peak stack use was measured through each task's worst case (an
ECDSA-checked install over Wi-Fi and from SD, get/put, a core dump
fetch, an IRC TLS handshake); stacks are now peak plus about 2 KB: loop
8 -> 6 KB, update 8 -> 5, storage 10 -> 6, irc 8 -> 6. The Debug Build's
console ring goes 6 -> 4 KB, serial TX 2 -> 1 KB, the GNSS UART buffer
1 KB -> 512 B.

On the device, with IRC on TLS: 46 KB free (was 31), an 18 KB low (was
9.4). The re-run of every worst case left at least 1.6 KB of stack free
in each task.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/services/gnss_service.cpp

@@ -32,7 +32,7 @@ void GnssService::start() {
 void GnssService::stop() { close(); }
 
 void GnssService::open(uint32_t nowMs) {
-    Serial1.setRxBufferSize(1024);  // before begin(): over 2 s of NMEA
+    Serial1.setRxBufferSize(512);  // before begin(): over a second of NMEA, read every 50 ms
     Serial1.begin(kBaud, SERIAL_8N1, kRxPin, kTxPin);
     open_ = true;
     active_ = false;  // tick() wakes it or puts it to sleep, per the setting

src/services/gnss_service.h

@@ -15,7 +15,7 @@
 namespace roro {
 
 // The GNSS receiver on the Cap LoRa-1262 (see CONTEXT.md and docs/milestones/M2.md): reads its
-// NMEA from the main loop's tick (about 450 bytes/s, so a 1 KB UART buffer covers any stall),
+// NMEA from the main loop's tick (about 450 bytes/s, so a 512-byte UART buffer covers a second),
 // holds the current Fix, and sets the clock from it. Settings → GNSS switches it on and off.
 class GnssService : public Service {
    public:

src/services/irc_service.cpp

@@ -33,7 +33,7 @@ IrcService::IrcService(KeyValueStore& store, const std::string& defaultNick, Wif
 void IrcService::start() {
     if (task_) return;
     lock_ = xSemaphoreCreateMutex();
-    xTaskCreate(taskEntry, "irc", 8192, this, 1, &task_);
+    xTaskCreate(taskEntry, "irc", 6144, this, 1, &task_);  // peak 4.0 KB (TLS handshake, M2)
 }
 
 void IrcService::connect() {

src/services/storage_service.cpp

@@ -14,7 +14,7 @@ namespace roro {
 
 void StorageService::start() {
     if (task_) return;
-    xTaskCreate(taskEntry, "storage", 10240, this, 1, &task_);  // room for a signature check
+    xTaskCreate(taskEntry, "storage", 6144, this, 1, &task_);  // peak 3.9 KB (SD install with its signature check, M2)
 }
 
 void StorageService::stop() {

src/services/update_service.cpp

@@ -90,7 +90,7 @@ void UpdateService::start() {
         store_.putString("ota_pending", "");
     }
 
-    if (!task_) xTaskCreate(taskEntry, "update", 8192, this, 1, &task_);
+    if (!task_) xTaskCreate(taskEntry, "update", 5120, this, 1, &task_);  // peak 3.4 KB (ECDSA check, M2)
 }
 
 void UpdateService::bootGuard(KeyValueStore& store) {