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)
+    }
+}

Sources/CLI/TerebiCLI.swift

@@ -20,6 +20,9 @@ enum TerebiCLI {
             }
             let app = executable.resolvingSymlinksInPath().deletingLastPathComponent()
                 .appendingPathComponent("terebi.app", isDirectory: true)
+            if let error = FFmpegRuntime.error(for: app) {
+                fail(error, code: 69)
+            }
             let configuration = NSWorkspace.OpenConfiguration()
             do {
                 // Launch without media first so SwiftUI creates its singleton window.

Sources/Launcher/FFmpegRuntime.swift

@@ -0,0 +1,39 @@
+import Foundation
+import Darwin
+
+enum FFmpegRuntime {
+    static func error(for app: URL) -> String? {
+        let manifest = app.appendingPathComponent("Contents/Resources/ffmpeg-libraries.txt")
+        let metadataError = "This app's FFmpeg library metadata is missing or invalid. Rebuild and reinstall terebi."
+        guard let contents = try? String(contentsOf: manifest, encoding: .utf8) else {
+            return metadataError
+        }
+        var paths = contents.components(separatedBy: "\n")
+        if paths.last == "" { paths.removeLast() }
+        let libraries: Set<String> = ["libavformat", "libavcodec", "libavutil", "libswresample", "libswscale"]
+        guard paths.count == libraries.count else { return metadataError }
+        var found = Set<String>()
+        for path in paths {
+            guard path.hasPrefix("/"), !path.contains("\0"), !path.contains("\r") else {
+                return metadataError
+            }
+            let parts = URL(fileURLWithPath: path).lastPathComponent.split(separator: ".", omittingEmptySubsequences: false)
+            guard parts.count >= 2, parts.last == "dylib" else { return metadataError }
+            let library = String(parts[0])
+            guard libraries.contains(library),
+                  parts.dropFirst().dropLast().allSatisfy({ !$0.isEmpty && $0.utf8.allSatisfy { (48...57).contains($0) } }),
+                  found.insert(library).inserted else {
+                return metadataError
+            }
+        }
+        for path in paths {
+            _ = dlerror()
+            guard dlopen(path, RTLD_NOW | RTLD_LOCAL) != nil else {
+                let detail = dlerror().map { String(cString: $0) } ?? "The dynamic loader could not load this library."
+                return "The FFmpeg libraries required by this build are unavailable or broken.\n\nRequired library: \(path)\n\(detail)\n\nInstall FFmpeg with `brew install ffmpeg`. If FFmpeg was upgraded or its library versions changed, rebuild and reinstall terebi."
+            }
+            // Deliberately never dlclose: retain successful loads until exit or bootstrap exec.
+        }
+        return nil
+    }
+}