Add converge-wake.service and systemd-sleep hook for wake-from-sleep sync

Creates a oneshot user service (converge-wake.service) that runs
converge --sync after the network is online, and a systemd-sleep hook
(/usr/lib/systemd/system-sleep/converge-wake) that triggers the service
for each logged-in user on resume.

Uses After=network-online.target for proper network timing on
NetworkManager/systemd-networkd setups, with a 5-second ExecStartPre
delay as a safety net for netctl and other environments where
network-online.target may not gate on resume.

Updated PKGBUILD and AGENTS.md accordingly.

AGENTS.md

@@ -18,9 +18,11 @@ test/TestHelper.hs   # Shared test utilities (temp repos, sentinel files)
 test/GitCommitSpec.hs   # Commit behaviour tests
 test/GitPullSpec.hs     # Pull/rebase tests
 test/GitSafetySpec.hs   # Operation-in-progress detection tests
-SPEC.md              # Human-readable specifications
-converge.example.yaml   # Example config file
-converge.service     # systemd unit file
+SPEC.md                 # Human-readable specifications
+converge.example.yaml    # Example config file
+converge.service         # systemd user service (daemon mode)
+converge-wake.service    # systemd user service (wake-from-sleep sync)
+src/system-sleep/        # systemd-sleep hook scripts
 ```
 
 ## Architecture