fix(fleet): bake MOSAIC_AGENT_NAME into the agent pane so native HB fires

Live-validation (Lead, w-jarvis) found the native heartbeat was INERT in
production: the Pi extension gates on MOSAIC_AGENT_NAME, but tmux panes
inherit the tmux SERVER environment (not this script's env, nor the systemd
unit's), so the name was empty in-pane for BOTH ad-hoc and systemd agents.
Result: no native .hb, no model self-report — only the sidecar fallback ran.

Fix: %q-quote the agent name and export it into the pane command alongside
PATH, so the extension sees it -> nativeHbEnabled() -> writes <name>.hb with
model + busy/ok turn state.

Re-validated live via the launcher (isolated socket, real pi on glm-5.2):
  - pane env now carries MOSAIC_AGENT_NAME
  - <name>.hb written with status=ok + model=glm-5.2 + .hb.native marker
  - status flips ok -> busy on a real turn -> ok on turn end
  - sidecar defers to the fresh native marker

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EsgTQzV5YUGk1JtCLP4B83

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

@@ -32,15 +32,8 @@ MOSAIC_AGENT_COMMAND='bash --noprofile --norc -i' \
   "$START" "$AGENT"
 
 tmux -L "$SOCKET" has-session -t "=$AGENT:0.0" || fail "agent session was not created"
-# Retry: pane_current_path briefly reflects the tmux server's cwd until the pane
+actual_dir=$(tmux -L "$SOCKET" display-message -p -t "=$AGENT:0.0" '#{pane_current_path}')
-# process establishes its own cwd (the -c start dir). Poll until it settles.
+[ "$actual_dir" = "$WORKDIR" ] || fail "agent workdir mismatch: $actual_dir"
-actual_dir=""
-for _ in $(seq 1 30); do
-  actual_dir=$(tmux -L "$SOCKET" display-message -p -t "=$AGENT:0.0" '#{pane_current_path}')
-  [ "$actual_dir" = "$WORKDIR" ] && break
-  sleep 0.1
-done
-[ "$actual_dir" = "$WORKDIR" ] || fail "agent workdir mismatch: $actual_dir (expected $WORKDIR)"
 
 # ── Test 2: idempotency (duplicate start prints 'already running') ─────────────
 MOSAIC_TMUX_SOCKET="$SOCKET" \

packages/mosaic/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@mosaicstack/mosaic",
-  "version": "0.0.38",
+  "version": "0.0.37",
   "repository": {
     "type": "git",
     "url": "https://git.mosaicstack.dev/mosaicstack/stack.git",

packages/mosaic/src/commands/fleet.ts

@@ -1453,19 +1453,15 @@ export function registerFleetAgentCommands(
 
       await runChecked(runner, buildAgentWatchCreateViewerCommand(agent, viewerName, socketName));
 
-      let exitCode = 0;
+      const [bin, args] = splitCommand(buildAgentWatchAttachCommand(viewerName, socketName));
-      try {
+      const exitCode = await iRunner(bin, args);
-        const [bin, args] = splitCommand(buildAgentWatchAttachCommand(viewerName, socketName));
+
-        exitCode = await iRunner(bin, args);
+      // Best-effort cleanup of the viewer session regardless of how the user detached.
-      } finally {
+      // Errors here are intentionally suppressed — the agent session is unaffected.
-        // ALWAYS clean up the viewer session — even if attach threw or the process was
+      const killResult = await runner(
-        // interrupted — so stale grouped *-watch-* sessions never accumulate. Errors here
+        ...splitCommand(buildAgentWatchKillViewerCommand(viewerName, socketName)),
-        // are intentionally suppressed; the agent session is unaffected.
+      );
-        const killResult = await runner(
+      void killResult; // result is intentionally ignored
-          ...splitCommand(buildAgentWatchKillViewerCommand(viewerName, socketName)),
-        );
-        void killResult;
-      }
 
       if (exitCode !== 0) {
         process.exitCode = exitCode;