fix: cron env missing DISINTO_CONTAINER=1, logs go to ro mount

Cron jobs run with minimal environment — no Docker compose env vars.
Without DISINTO_CONTAINER=1, env.sh falls back to FACTORY_ROOT for
log paths, which is the read-only disinto mount. Polls silently fail.

Fix: set DISINTO_CONTAINER=1 as crontab environment variable.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docker/agents/entrypoint.sh

@@ -18,7 +18,7 @@ log() {
 
 # Build crontab from project TOMLs and install for the agent user.
 install_project_crons() {
-  local cron_lines=""
+  local cron_lines="DISINTO_CONTAINER=1"
   for toml in "${DISINTO_DIR}"/projects/*.toml; do
     [ -f "$toml" ] || continue
     local pname