Make delivery and integration failures explicit

Persist reminder presentations and retry state, atomically complete collapsed deliveries, fall back across away reaches, and block permanent failures visibly (V-715, V-678). Fail closed when enabled integrations lack credentials and keep remote arms explicitly dark (V-691). Give mavweb one sanitized, request-correlated error contract (V-689). Owner explicitly requested direct commits to master.

docker-compose.yml

@@ -97,15 +97,17 @@ services:
     <<: *image
     # voice.bind is 0.0.0.0:9100 in deploy/mavend.json so mavweb can reach it
     # cross-container. Verified 2026-07-06.
-    # -ambient-token turns on POST /api/ambient (Vikunja #126): the phone posts
-    # notification text, mavweb keeps only a meeting time. Empty ⇒ no route at
-    # all, which is what a missing MAVEN_AMBIENT_TOKEN gives. The value comes
-    # from the gitignored .env docker compose reads for interpolation, NOT from
-    # an env_file — flags are interpolated before any service env exists.
+    # -ambient-enabled turns on POST /api/ambient (Vikunja #126): the phone posts
+    # notification text, mavweb keeps only a meeting time. The explicit enabled
+    # flag prevents an unset token from looking like an intentional dark state.
+    # Both values come from the gitignored .env docker compose reads for
+    # interpolation, NOT from an env_file — flags are interpolated before any
+    # service env exists.
     # Weakness worth naming: mavweb takes this as a flag, so it is visible in
     # `ps` inside this container, unlike the zenmoney and IMAP secrets which are
     # read from files.
     command: ["mavweb", "-addr", ":9201", "-voice", "mavend:9100", "-core", "/run/maven/mavend.sock",
+              "-ambient-enabled", "${MAVEN_AMBIENT_ENABLED:-false}",
               "-ambient-token", "${MAVEN_AMBIENT_TOKEN:-}",
               "-nexus", "http://nexus:9740", "-praxis", "http://praxis:8989", "-hexis", "http://hexis:9741"]
     depends_on: [mavend]