M1 step 4b: IRC Service on the device; 8-bit frame buffer

- IrcService: networking on its own task, TLS with the built-in CA
  bundle (or trust-on-first-use pinning when self-signed is allowed),
  plain TCP when TLS is off; connects only while Wi-Fi is Connected,
  marks pauses for Monitoring, reconnects with backoff, pings a quiet
  server, writes Logs, raises Notifications for Mentions
- Session: forget /quit once disconnected (it was handled every loop);
  the server Buffer never counts as unread (MOTD showed as [4])
- Status Bar: unread count
- Frame buffer 16 -> 8-bit colour (M1 Q46): min free heap with IRC on
  TLS went from 51 KB to 79 KB
- Serial: irc start / say / dump

Verified on the device against irc.libera.chat:6697: certificate
checked, joined #roro9stack-test, sent a message, quit cleanly.

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

src/ui/screen.cpp

@@ -5,7 +5,7 @@
 namespace roro {
 
 bool Screen::begin() {
-    canvas_.setColorDepth(16);
+    canvas_.setColorDepth(8);  // RGB332: saves 32 KB of RAM (M1 Q46); theme colours are converted
     canvas_.setPsram(false);
     return canvas_.createSprite(theme::kWidth, theme::kHeight) != nullptr;
 }

src/ui/screen.h

@@ -9,7 +9,7 @@ namespace roro {
 // Composes the frame (Status Bar, foreground App, Toast) off-screen and pushes it to the display.
 class Screen {
    public:
-    bool begin();  // allocates the frame buffer (~64 KB)
+    bool begin();  // allocates the frame buffer (~32 KB at 8-bit colour)
     void render(AppManager& apps, const StatusInfo& status, const Toast* toast);
     Canvas& canvas() { return canvas_; }
 

src/ui/widgets.cpp

@@ -29,6 +29,7 @@ void statusBar(Canvas& c, const StatusInfo& info) {
         x -= c.textWidth(text.c_str()) + 6;
     };
     right(info.clock, kText);
+    if (info.unread > 0) right("[" + std::to_string(info.unread) + "]", kMessage);
     if (info.batteryPercent >= 0)
         right(std::to_string(info.batteryPercent) + "%", info.batteryPercent <= 15 ? kWarning : kText);
     if (info.sdPresent) right("SD", info.sdLevel >= 80 ? kWarning : kMuted);

src/ui/widgets.h

@@ -23,11 +23,12 @@ struct StatusInfo {
     char compose = 0;  // pending Compose Key state
     enum class Wifi { None, Searching, Connected, Monitoring } wifi = Wifi::None;
     int wifiBars = 0;  // 0..3 when Connected
+    int unread = 0;    // unread messages across Services
 
     bool operator==(const StatusInfo& o) const {
         return title == o.title && batteryPercent == o.batteryPercent && clock == o.clock &&
                sdPresent == o.sdPresent && sdLevel == o.sdLevel && compose == o.compose && wifi == o.wifi &&
-               wifiBars == o.wifiBars;
+               wifiBars == o.wifiBars && unread == o.unread;
     }
     bool operator!=(const StatusInfo& o) const { return !(*this == o); }
 };