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/node/src/commands/init.ts

@@ -258,7 +258,10 @@ export async function runInit(
 	const { isAgentMode } = await import("../state.js");
 	const { captureEvent } = await import("../telemetry.js");
 
-	const fireInit = (mode: "agent" | "email" | "api_key" | "existing_key", claimed = false) => {
+	const fireInit = (
+		mode: "agent" | "email" | "api_key" | "existing_key",
+		claimed = false,
+	) => {
 		const props: Record<string, unknown> = { command: "init", mode };
 		const caller = detectAgentCaller();
 		if (caller) props.agent_caller = caller;
@@ -286,7 +289,12 @@ export async function runInit(
 	}
 
 	// ── Claim flow: --email against an existing agent-mode config ───────────
-	if (opts.email && fs.existsSync(CONFIG_FILE) && savedConfig.platform.agentMode && savedConfig.platform.apiKey) {
+	if (
+		opts.email &&
+		fs.existsSync(CONFIG_FILE) &&
+		savedConfig.platform.agentMode &&
+		savedConfig.platform.apiKey
+	) {
 		const email = opts.email.trim().toLowerCase();
 		validateEmail(email);
 		printInfo(`Claiming Agent Mode account to ${email}...`);
@@ -370,9 +378,7 @@ export async function runInit(
 	// recognized agent env var. Pure "no TTY" alone is NOT enough — pipe
 	// users would get surprised by a silent shadow signup.
 	const agentCtx =
-		opts.agent === true ||
-		isAgentMode() ||
-		detectAgentCaller() !== null;
+		opts.agent === true || isAgentMode() || detectAgentCaller() !== null;
 	if (!opts.apiKey && !opts.email && agentCtx) {
 		await bootstrapViaBackend(config, { source: opts.source ?? null });
 		fireInit("agent");