feat: install release builds and report missing FFmpeg

Add make release and make install PREFIX=/Users/valdemar/.local. Keep optimized no-debug release artifacts separate; install adjacent CLI/app under lib/terebi and link bin/terebi. Preflight FFmpeg/pkg-config before compiling or installing, including cached builds.

Record the player's exact linked FFmpeg ABI paths. AppKit-only CLI/bootstrap validate native loadability and transitive dependencies before entering the FFmpeg-linked terebi-player. CLI fails with status 69 and remediation; Finder bootstrap shows a native alert and execs the player without losing initial events or process identity.

Verified staged installation with spaces, reinstall preservation, absent build dependencies, missing/corrupt/transitively broken dylibs, real modal error surface, installed CLI and Finder startup across exec, local/YouTube resume and window reuse, and full make check.

Sources/App/Bootstrap.swift

@@ -0,0 +1,34 @@
+import AppKit
+import Darwin
+
+@main
+@MainActor
+enum TerebiBootstrap {
+    static func main() {
+        let app = Bundle.main.bundleURL
+        if let error = FFmpegRuntime.error(for: app) {
+            fail(error)
+        }
+        let payload = app.appendingPathComponent("Contents/MacOS/terebi-player")
+        let errorCode = payload.path.withCString { path in
+            _ = execv(path, CommandLine.unsafeArgv)
+            return errno
+        }
+        let detail = String(cString: strerror(errorCode))
+        fail("Could not start the player: \(detail)\n\nPlayer executable: \(payload.path)\nRebuild and reinstall terebi.")
+    }
+
+    private static func fail(_ message: String) -> Never {
+        FileHandle.standardError.write(Data("terebi: \(message)\n".utf8))
+        let application = NSApplication.shared
+        application.setActivationPolicy(.regular)
+        application.activate(ignoringOtherApps: true)
+        let alert = NSAlert()
+        alert.alertStyle = .critical
+        alert.messageText = "terebi could not start"
+        alert.informativeText = message
+        alert.addButton(withTitle: "Quit")
+        alert.runModal()
+        exit(69)
+    }
+}