Implement Cast Streaming mirroring, DLNA casting, daemon+GUI, and breadd integration

Builds out the full v1 scope: a vendored+patched openscreen subset for
low-latency Cast Streaming (Mirroring receiver 0F5096E8) alongside the
existing Cast V2/HLS and new DLNA/AVTransport casting paths, breadcastd's
Idle/Casting state machine with a private IPC socket, the breadcast GTK4
popup as a thin IPC client, and bread.cast.*/bread.command.cast.* breadd
integration (device discovery, start/stop, mirroring lifecycle events).
Also adds bakery/systemd/Forgejo CI packaging.

Validated end-to-end against a real Chromecast/Google TV: negotiated
Cast Streaming session, live pipeline playback, and daemon+GUI click-to-cast/
stop through the actual popup.

breadcast-caststream-sys/vendor/openscreen/cast/streaming/public/frame_id.h

@@ -0,0 +1,121 @@
+// Copyright 2016 The Chromium Authors
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CAST_STREAMING_PUBLIC_FRAME_ID_H_
+#define CAST_STREAMING_PUBLIC_FRAME_ID_H_
+
+#include <stdint.h>
+
+#include <limits>
+#include <sstream>
+#include <string>
+
+#include "cast/streaming/impl/expanded_value_base.h"
+
+namespace openscreen::cast {
+
+// Forward declaration (see below).
+class FrameId;
+
+// Convenience operator overloads for logging.
+std::ostream& operator<<(std::ostream& out, const FrameId rhs);
+
+// Unique identifier for a frame in a RTP media stream.  FrameIds are truncated
+// to 8-bit values in RTP and RTCP headers, and then expanded back by the other
+// endpoint when parsing the headers.
+//
+// Usage example:
+//
+//   // Distance/offset math.
+//   FrameId first = FrameId::first();
+//   FrameId second = first + 1;
+//   FrameId third = second + 1;
+//   int64_t offset = third - first;
+//   FrameId fourth = second + offset;
+//
+//   // Logging convenience.
+//   OSP_DLOG_INFO << "The current frame is " << fourth;
+class FrameId : public ExpandedValueBase<int64_t, FrameId> {
+ public:
+  // The "null" FrameId constructor.  Represents a FrameId field that has not
+  // been set and/or a "not applicable" indicator.
+  constexpr FrameId() : FrameId(std::numeric_limits<int64_t>::min()) {}
+
+  constexpr explicit FrameId(int64_t value) : ExpandedValueBase(value) {}
+
+  // Allow copy construction and assignment.
+  constexpr FrameId(const FrameId&) = default;
+  constexpr FrameId& operator=(const FrameId&) = default;
+
+  // Returns true if this is the special value representing null.
+  constexpr bool is_null() const { return *this == FrameId(); }
+
+  // Distance operator.
+  int64_t operator-(FrameId rhs) const {
+    OSP_CHECK(!is_null());
+    OSP_CHECK(!rhs.is_null());
+    return value_ - rhs.value_;
+  }
+
+  // Operators to compute advancement by incremental amounts.
+  constexpr FrameId operator+(int64_t rhs) const {
+    OSP_CHECK(!is_null());
+    return FrameId(value_ + rhs);
+  }
+  constexpr FrameId operator-(int64_t rhs) const {
+    OSP_CHECK(!is_null());
+    return FrameId(value_ - rhs);
+  }
+  constexpr FrameId& operator+=(int64_t rhs) {
+    OSP_CHECK(!is_null());
+    return (*this = (*this + rhs));
+  }
+  constexpr FrameId& operator-=(int64_t rhs) {
+    OSP_CHECK(!is_null());
+    return (*this = (*this - rhs));
+  }
+  constexpr FrameId& operator++() {
+    OSP_CHECK(!is_null());
+    ++value_;
+    return *this;
+  }
+  constexpr FrameId& operator--() {
+    OSP_CHECK(!is_null());
+    --value_;
+    return *this;
+  }
+  constexpr FrameId operator++(int) {
+    OSP_CHECK(!is_null());
+    return FrameId(value_++);
+  }
+  constexpr FrameId operator--(int) {
+    OSP_CHECK(!is_null());
+    return FrameId(value_--);
+  }
+
+  // The identifier for the first frame in a stream.
+  static constexpr FrameId first() { return FrameId(0); }
+
+  // A virtual identifier, representing the frame before the first. There should
+  // never actually be a frame streamed with this identifier. Instead, this is
+  // used in various components to represent a "not yet seen/processed the first
+  // frame" state.
+  //
+  // The name "leader" comes from the terminology used in tape reels, which
+  // refers to the non-data-carrying segment of tape before the recording
+  // begins.
+  static constexpr FrameId leader() { return FrameId(-1); }
+
+  constexpr int64_t value() const { return value_; }
+
+  std::string ToString() const;
+
+ private:
+  friend class ExpandedValueBase<int64_t, FrameId>;
+  friend std::ostream& operator<<(std::ostream& out, const FrameId rhs);
+};
+
+}  // namespace openscreen::cast
+
+#endif  // CAST_STREAMING_PUBLIC_FRAME_ID_H_