AgentAPI can now save and restore conversation state across workspace
restarts. The module exports env vars (AGENTAPI_STATE_FILE,
AGENTAPI_SAVE_STATE, AGENTAPI_LOAD_STATE, AGENTAPI_PID_FILE) that the
binary reads directly. No consumer module changes needed.
New variables: enable_state_persistence (default false),
state_file_path, pid_file_path. State and PID files default to
$HOME/<module_dir_name>/.
Requires agentapi >= v0.12.0. A shared version_at_least function in
lib.sh gates the env var exports and SIGUSR1 in the shutdown script.
Old binaries get a warning and graceful skip.
Shutdown script now does SIGUSR1 (state save), log snapshot capture
(existing, now fault-tolerant via subshell), then SIGTERM with wait.
Closes coder/internal#1257
Refs coder/internal#1256
Refs #696
2169fb00ee