feat: add shared TTY progress bars for ZED offline tools

Extract the tqdm-like stderr progress bar into a shared helper and reuse it across zed_svo_to_mp4, zed_svo_grid_to_mp4, and zed_svo_to_mcap.

For zed_svo_to_mcap, single-source exports now report exact frame totals and bundled multi-camera exports report exact synced-group totals on TTY. When bundled mode runs without --end-frame, the tool performs a counting pass first so the progress total remains exact instead of estimated.

Also document the bundled MCAP progress behavior in the README and record the current third_party dependency state in third_party/README. That note now makes it explicit that CLI11 and proxy are the active submodules, while tomlplusplus and mcap are vendored source drops, and adds a TODO to revisit converting mcap into a submodule later.

Verified with the Debug build during implementation, including single-camera and bundled zed_svo_to_mcap runs that rendered clean progress output to a TTY.

include/cvmmap_streamer/tools/zed_progress_bar.hpp

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cstdint>
+#include <memory>
+
+namespace cvmmap_streamer::zed_tools {
+
+[[nodiscard]]
+bool stderr_supports_progress_bar();
+
+class ProgressBar {
+public:
+	explicit ProgressBar(std::uint64_t total_frames);
+	~ProgressBar();
+
+	[[nodiscard]]
+	bool enabled() const;
+
+	void update(std::uint64_t completed_frames);
+	void finish(std::uint64_t completed_frames, bool success);
+
+private:
+	struct Impl;
+	std::unique_ptr<Impl> impl_{};
+};
+
+}  // namespace cvmmap_streamer::zed_tools