fix(lib): handle agent_not_ready startup state and reject claude fullscreen upsell modal

- Accept agent_not_ready from herdr agent start to allow startup dialog handling without premature rollback, while preserving fail-closed behavior on dead process timeouts.
- Match Claude fullscreen renderer upsell modal via 'Yes, try it' and dismiss with Escape to avoid dropping permission flags or deadlocking on idle /tui tips.
- Add behavioral test suite in test_b19_headless_reconcile_fixes.py and cross-agent review reports.

tests/test_b19_headless_reconcile_fixes.py

@@ -3,6 +3,7 @@ import sys
 import json
 import subprocess
 import time
+from pathlib import Path
 import pytest
 
 from lib_py.layout import compute_2xk_layout
@@ -101,6 +102,111 @@ def test_bug4_send_keys_safe_gating_order():
     assert dialog_idx < prompt_idx, "_pane_dialog_open must execute before agent prompt fast-path"
 
 
+_LIB_SH = str(Path(__file__).resolve().parent.parent / ".agents" / "skills" / "lib.sh")
+
+_FULLSCREEN_TIP = """Claude Code
+Try the new fullscreen renderer — flicker-free output, mouse support, auto-copy on select · /tui fullscreen
+❯
+"""
+
+_FULLSCREEN_MODAL = """Try the new fullscreen renderer?
+Flicker-free output
+Selected text auto-copies to your clipboard
+Yes, try it
+"""
+
+
+def _run_lib_helpers(script_body, env_extra=None):
+    env = dict(os.environ)
+    if env_extra:
+        env.update(env_extra)
+    wrapper = f"""
+set -euo pipefail
+source "{_LIB_SH}"
+_init_herdr_isolation() {{ :; }}
+{script_body}
+"""
+    return subprocess.run(["bash", "-c", wrapper], capture_output=True, text=True, env=env)
+
+
+def test_agent_start_success_tokens_exclude_startup_timeout():
+    """D-1: dead-process timeout must not be promoted to success; agent_not_ready may."""
+    content = open(_LIB_SH, encoding="utf-8").read()
+    success_line = next(l for l in content.splitlines()
+                        if 'grep -qE "agent_started' in l)
+    assert "agent_not_ready" in success_line
+    assert "timed out waiting for agent startup" not in success_line
+    err_line = next(i for i, l in enumerate(content.splitlines())
+                    if 'grep -qiE "^usage:' in l)
+    ok_line = next(i for i, l in enumerate(content.splitlines())
+                   if 'grep -qE "agent_started' in l)
+    assert err_line < ok_line
+
+
+def test_fullscreen_tip_is_not_a_blocking_dialog():
+    """D-2: idle /tui fullscreen tip must not trip _pane_dialog_open or send keys."""
+    script = f"""
+_pane_capture() {{ printf '%s' '{_FULLSCREEN_TIP}'; }}
+KEYS=/tmp/mam-fs-tip-keys.$$
+: > "$KEYS"
+_sks_herdr() {{
+  if [ "${{1:-}}" = "send-keys" ]; then echo "$*" >> "$KEYS"; fi
+  return 0
+}}
+if _pane_dialog_open dummy; then echo "DIALOG_OPEN"; else echo "DIALOG_CLOSED"; fi
+handle_startup_dialogs dummy 2
+echo "KEYS_CONTENT=$(tr '\\n' '|' < "$KEYS")"
+rm -f "$KEYS"
+"""
+    res = _run_lib_helpers(script)
+    assert res.returncode == 0, res.stderr + res.stdout
+    assert "DIALOG_CLOSED" in res.stdout
+    assert "Escape" not in res.stdout
+    assert "Enter" not in res.stdout.split("KEYS_CONTENT=")[-1]
+
+
+def test_fullscreen_modal_is_rejected_not_accepted():
+    """D-3: Yes, try it modal is a dialog; dismiss with Escape, never Enter."""
+    script = f"""
+_pane_capture() {{ printf '%s' '{_FULLSCREEN_MODAL}'; }}
+KEYS=/tmp/mam-fs-modal-keys.$$
+: > "$KEYS"
+_sks_herdr() {{
+  if [ "${{1:-}}" = "send-keys" ]; then echo "$*" >> "$KEYS"; fi
+  return 0
+}}
+if _pane_dialog_open dummy; then echo "DIALOG_OPEN"; else echo "DIALOG_CLOSED"; fi
+handle_startup_dialogs dummy 1
+echo "KEYS_CONTENT=$(tr '\\n' '|' < "$KEYS")"
+rm -f "$KEYS"
+"""
+    res = _run_lib_helpers(script)
+    assert res.returncode == 0, res.stderr + res.stdout
+    assert "DIALOG_OPEN" in res.stdout
+    keys = res.stdout.split("KEYS_CONTENT=")[-1]
+    assert "Escape" in keys
+    assert "Enter" not in keys
+
+
+def test_wait_for_tui_ready_succeeds_on_fullscreen_tip():
+    """D-2c: tip + ready banner must not deadlock wait_for_tui_ready."""
+    script = f"""
+_pane_capture() {{ printf '%s' '{_FULLSCREEN_TIP}'; }}
+_sks_herdr() {{
+  if [ "${{1:-}}" = "capture-pane" ]; then printf '%s' '{_FULLSCREEN_TIP}'; return 0; fi
+  if [ "${{1:-}}" = "send-keys" ]; then echo "KEY:$*" >&2; return 0; fi
+  return 0
+}}
+sleep() {{ :; }}
+export MAM_READY_TOKENS='Claude Code|Welcome'
+wait_for_tui_ready dummy-sess claude
+"""
+    res = _run_lib_helpers(script)
+    assert res.returncode == 0, res.stderr + res.stdout
+    assert "TUI detected ready" in res.stdout
+    assert "KEY:" not in res.stderr
+
+
 def test_bug4_no_duplicate_input_on_rpc_success(tmp_path):
     """Verify Bug 4: when herdr agent prompt succeeds, send_keys_safe returns 0 without calling paste-buffer."""
     test_script = f"""#!/usr/bin/env bash