Add launchd LaunchAgent for macOS (systemd equivalent)

com.odysseus.ui.plist + install-service-macos.sh run Odysseus at login
and restart on crash, the macOS counterpart to odysseus-ui.service. The
installer auto-fills paths from the venv, so there's no hand-editing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

com.odysseus.ui.plist

@@ -0,0 +1,42 @@
+<?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">
+<!--
+  macOS launchd equivalent of odysseus-ui.service (systemd).
+
+  Do not edit the __PLACEHOLDERS__ by hand — run ./install-service-macos.sh,
+  which fills them in from your venv/install path and loads the agent. This is
+  a per-user LaunchAgent: it runs at login, needs no sudo, and restarts the
+  server if it crashes (KeepAlive). The app reads .env itself via python-dotenv,
+  so there's no EnvironmentFile to wire up.
+-->
+<plist version="1.0">
+<dict>
+    <key>Label</key>
+    <string>com.odysseus.ui</string>
+
+    <key>ProgramArguments</key>
+    <array>
+        <string>__UVICORN__</string>
+        <string>app:app</string>
+        <string>--host</string>
+        <string>__HOST__</string>
+        <string>--port</string>
+        <string>__PORT__</string>
+    </array>
+
+    <key>WorkingDirectory</key>
+    <string>__WORKDIR__</string>
+
+    <key>RunAtLoad</key>
+    <true/>
+
+    <!-- Restart on crash (systemd Restart=always equivalent). -->
+    <key>KeepAlive</key>
+    <true/>
+
+    <key>StandardOutPath</key>
+    <string>__LOGDIR__/odysseus.out.log</string>
+    <key>StandardErrorPath</key>
+    <string>__LOGDIR__/odysseus.err.log</string>
+</dict>
+</plist>