fix(fleet): export MOSAIC_AGENT_CLASS into the agent pane so personas inject (#669)

packages/mosaic/framework/tools/fleet/test-start-agent-session.sh

@@ -104,6 +104,7 @@ PATH="$FAKE_BIN:$PATH" \
 MOSAIC_TMUX_SOCKET="$SOCKET3" \
 MOSAIC_AGENT_WORKDIR="$WORKDIR3" \
 MOSAIC_AGENT_RUNTIME="pi" \
+MOSAIC_AGENT_CLASS="code" \
 MOSAIC_RUNTIME_BIN="$FAKE_RUNTIME_BIN" \
 MOSAIC_AGENT_COMMAND="mosaic yolo pi --model openai-codex/gpt-5.5:high" \
 MOSAIC_HEARTBEAT_RUN_DIR="$HB_RUN_DIR3" \
@@ -127,6 +128,18 @@ echo "$all_args" | grep -qF "exec " || fail "pane command does not use exec"
 echo "$all_args" | grep -qF "mosaic yolo pi --model openai-codex/gpt-5.5:high" || \
   fail "pane command does not forward MOSAIC_AGENT_COMMAND with flags intact"
 
+# d) MOSAIC_AGENT_NAME and the per-agent MOSAIC_AGENT_CLASS must BOTH be exported
+#    INTO the pane. The pane inherits the tmux SERVER environment (not this
+#    script's env, nor the systemd unit's EnvironmentFile), so any per-agent var
+#    the launcher needs in-pane must be re-exported in the snippet. CLASS is
+#    load-bearing: the launcher composes the persona contract from
+#    process.env.MOSAIC_AGENT_CLASS, so a missing export silently drops the
+#    persona (regression guard for the A3a pane-propagation gap).
+echo "$all_args" | grep -qF "export MOSAIC_AGENT_NAME=" || \
+  fail "pane command does not export MOSAIC_AGENT_NAME into the pane"
+echo "$all_args" | grep -qF "export MOSAIC_AGENT_CLASS=code" || \
+  fail "pane command does not export MOSAIC_AGENT_CLASS into the pane (persona would silently drop)"
+
 # ── Test 4: when no extra runtime-bin dirs exist, exec still appears ───────────
 TMUX_ARGS_FILE2=$(mktemp)
 FAKE_BIN2=$(mktemp -d)