Surface mem0_notice for unclaimed Agent Mode keys + docs

CLI now consumes the unified mem0_notice surface that the platform side
emits for unclaimed Agent Mode keys. The notice is a directive to the
LLM agent reading the output, with a verbatim sentence to relay to the
human owner. Two presentation paths:

- Human/text output: yellow stderr banner after the primary output,
  once per command. Skipped in agent mode (the JSON envelope carries
  it instead, so no duplication).
- JSON/agent output (--json/--agent): folded into the envelope as
  "mem0_notice" so an agent parsing the output sees it without
  inspecting HTTP headers.

CLI changes (Python + Node, kept in lockstep):
- state.{ts,py}: captureNotice / takeNotice helpers — last-write-wins
  stash so multi-request commands fire the notice exactly once.
- backend/platform.{ts,py}: _request extracts notice from response
  bodies (top-level dict or list[0]) with header fallback, strips
  from downstream payload, captures for end-of-command surfacing.
- output.{ts,py}: JSON envelope formatters fold in any pending notice.
- index.ts / app.py: entrypoint surfaces notice on exit when not in
  agent mode.
- commands/agent-mode.{ts,py}: init success path prints the platform's
  notice verbatim (fallback to dim claim-command line if a stale
  backend doesn't return it).

Init-flag handling fix: the Python argv preprocessor was stripping
--agent from sys.argv unconditionally as the global JSON-output alias.
That swallowed `mem0 init --agent` (where --agent is a subcommand flag
for unattended bootstrap). Now preserved when "init" is in argv.

Parity tests: cli/python/tests/test_agent_mode.py and
cli/node/tests/agent-mode.test.ts — 7 tests each, kept in sync.

cli-spec.json updated: init now lists --agent and --source.

Docs:
- README.md: Agent Mode promo at top of Quickstart.
- docs/llms.txt: fast-path block for AI agents reading the docs.
- skills/mem0/SKILL.md, skills/mem0-cli/SKILL.md,
  skills/mem0-integrate/SKILL.md, mem0-plugin/skills/mem0/SKILL.md:
  autonomous-setup section + fallback hints.
- mem0-plugin/README.md, openclaw/README.md: "Quick path for agents"
  blocks above the human Quick Start.

cli/python/src/mem0_cli/app.py

@@ -856,7 +856,9 @@ def init(
         False, "--agent", help="Bootstrap an unattended Agent Mode account (no email required)."
     ),
     source: str | None = typer.Option(
-        None, "--source", help="Channel attribution for signup (e.g. github, hn, ph).",
+        None,
+        "--source",
+        help="Channel attribution for signup (e.g. github, hn, ph).",
     ),
 ) -> None:
     """Interactive setup wizard for mem0 CLI.
@@ -1215,11 +1217,28 @@ def main() -> None:
     import sys
 
     # Allow --json/--agent anywhere in the command line (not just before subcommand).
-    _json_flags = {"--json", "--agent"}
-    if any(a in _json_flags for a in sys.argv[1:]):
+    # Special case: `mem0 init --agent` is a subcommand flag (Agent Mode bootstrap)
+    # consumed by init_cmd, not a global JSON-output toggle — leave it in argv.
+    argv_rest = sys.argv[1:]
+    is_init = "init" in argv_rest
+    _global_flags = {"--json"} if is_init else {"--json", "--agent"}
+    if any(a in _global_flags for a in argv_rest):
         from mem0_cli.state import set_agent_mode
 
         set_agent_mode(True)
-        sys.argv = [sys.argv[0]] + [a for a in sys.argv[1:] if a not in _json_flags]
+        sys.argv = [sys.argv[0]] + [a for a in argv_rest if a not in _global_flags]
 
-    app()
+    try:
+        app()
+    finally:
+        # Surface any unclaimed Agent Mode notice once per command, after the
+        # primary output. In JSON/agent mode the notice is folded into the
+        # envelope by format_json_envelope, so skip the stderr banner there
+        # to avoid duplicate output.
+        from mem0_cli.state import is_agent_mode, take_notice
+
+        notice = take_notice()
+        if notice and not is_agent_mode():
+            from rich.console import Console
+
+            Console(stderr=True).print(f"\n[yellow]🔔 {notice}[/yellow]\n")