add microphone capture and stable code signing for TCC persistence

Adds --capture-mic/--mic-output for a second, independently-captured audio
track (mic vs system, written to separate outputs to avoid interleaving
corruption). Embeds Info.plist at link time so the binary carries a stable
CFBundleIdentifier and the usage-description keys TCC requires, and adds
scripts/build-signed.sh + scripts/create-signing-identity.sh so a rebuilt
binary keeps the same signing identity instead of losing granted
permissions on every rebuild.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Sources/AudioTeeCLI/Info.plist

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleIdentifier</key>
+	<string>com.stephanetailland.audiotee</string>
+	<key>CFBundleName</key>
+	<string>audiotee</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>NSAudioCaptureUsageDescription</key>
+	<string>audiotee captures system audio for local, on-device meeting transcription.</string>
+	<key>NSMicrophoneUsageDescription</key>
+	<string>audiotee captures microphone audio for local, on-device meeting transcription.</string>
+</dict>
+</plist>