feat: port upstream PRs #852, #965, #972, #971, #977, #975

Port 6 upstream PRs (PR #939 was already ported):

- #852: Complete HalPowerManager with RAII Lock class, WiFi check in
  setPowerSaving, skipLoopDelay overrides for ClearCache/OtaUpdate,
  and power lock in Activity render task loops
- #965: Fix paragraph formatting inside list items by tracking
  listItemUntilDepth to prevent unwanted line breaks
- #972: Micro-optimizations: std::move in insertFont, const ref for
  getDataFromBook parameter
- #971: Remove redundant hasPrintableChars pre-rendering pass from
  EpdFont, EpdFontFamily, and GfxRenderer
- #977: Skip unsupported image formats before extraction, add
  PARSE_BUFFER_SIZE constant and chapter parse timing
- #975: Fix UITheme memory leak by replacing raw pointer with
  std::unique_ptr for currentTheme

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/hal/HalPowerManager.cpp

@@ -1,6 +1,7 @@
 #include "HalPowerManager.h"
 
 #include <Logging.h>
+#include <WiFi.h>
 #include <esp_sleep.h>
 
 #include "HalGPIO.h"
@@ -8,12 +9,27 @@
 void HalPowerManager::begin() {
   pinMode(BAT_GPIO0, INPUT);
   normalFreq = getCpuFrequencyMhz();
+  modeMutex = xSemaphoreCreateMutex();
+  assert(modeMutex != nullptr);
 }
 
 void HalPowerManager::setPowerSaving(bool enabled) {
   if (normalFreq <= 0) {
-    return;  // invalid state
+    return;
   }
+
+  if (enabled) {
+    if (WiFi.getMode() != WIFI_MODE_NULL) {
+      enabled = false;
+    }
+    xSemaphoreTake(modeMutex, portMAX_DELAY);
+    const LockMode mode = currentLockMode;
+    xSemaphoreGive(modeMutex);
+    if (mode == NormalSpeed) {
+      enabled = false;
+    }
+  }
+
   if (enabled && !isLowPower) {
     LOG_DBG("PWR", "Going to low-power mode");
     if (!setCpuFrequencyMhz(LOW_POWER_FREQ)) {
@@ -31,6 +47,25 @@ void HalPowerManager::setPowerSaving(bool enabled) {
   isLowPower = enabled;
 }
 
+// RAII Lock implementation
+
+HalPowerManager::Lock::Lock() {
+  xSemaphoreTake(powerManager.modeMutex, portMAX_DELAY);
+  powerManager.currentLockMode = NormalSpeed;
+  valid = true;
+  if (powerManager.isLowPower) {
+    powerManager.setPowerSaving(false);
+  }
+  xSemaphoreGive(powerManager.modeMutex);
+}
+
+HalPowerManager::Lock::~Lock() {
+  if (!valid) return;
+  xSemaphoreTake(powerManager.modeMutex, portMAX_DELAY);
+  powerManager.currentLockMode = None;
+  xSemaphoreGive(powerManager.modeMutex);
+}
+
 void HalPowerManager::startDeepSleep(HalGPIO& gpio) const {
   // Ensure that the power button has been released to avoid immediately turning back on if you're holding it
   while (gpio.isPressed(HalGPIO::BTN_POWER)) {