[launchd] Sync Claude session state on macOS

Adds a launchd agent that runs the existing claude-save make target
every 30 minutes and at login, so macOS machines commit and push
session state the way the systemd timer does on Linux.

The agent runs through /bin/sh because launchd expands neither ~ nor
$HOME in ProgramArguments, and sets PATH explicitly because agents
inherit no shell environment. The claude target loads it via launchctl
bootstrap on darwin.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Makefile

@@ -45,6 +45,11 @@ claude:
 		systemctl --user daemon-reload && \
 		systemctl --user enable --now claude-save.timer; \
 	fi
+	@if [ $(OS_NAME) = "darwin" ]; then \
+		launchctl bootout gui/$$(id -u)/com.powellc.claude-save 2>/dev/null; \
+		launchctl bootstrap gui/$$(id -u) ~/Library/LaunchAgents/com.powellc.claude-save.plist && \
+		echo "claude: loaded com.powellc.claude-save"; \
+	fi
 
 claude-save:
 	@cd $(CLAUDE_HISTORY_DIR) && \

launchd/Library/LaunchAgents/com.powellc.claude-save.plist

@@ -0,0 +1,35 @@
+<?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>Label</key>
+    <string>com.powellc.claude-save</string>
+
+    <!-- sh expands $HOME; launchd does not expand ~ in ProgramArguments -->
+    <key>ProgramArguments</key>
+    <array>
+        <string>/bin/sh</string>
+        <string>-c</string>
+        <string>make -C "$HOME/.dotfiles" claude-save</string>
+    </array>
+
+    <key>EnvironmentVariables</key>
+    <dict>
+        <key>PATH</key>
+        <string>/opt/homebrew/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin</string>
+    </dict>
+
+    <key>StartInterval</key>
+    <integer>1800</integer>
+
+    <key>RunAtLoad</key>
+    <true/>
+
+    <key>StandardOutPath</key>
+    <string>/tmp/claude-save.out</string>
+
+    <key>StandardErrorPath</key>
+    <string>/tmp/claude-save.err</string>
+</dict>
+</plist>