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/output.ts

@@ -5,6 +5,7 @@
 import boxen from "boxen";
 import Table from "cli-table3";
 import { colors, sym } from "./branding.js";
+import { takeNotice } from "./state.js";
 
 const { brand, accent, success, error: errorColor, dim } = colors;
 
@@ -244,6 +245,15 @@ export function formatJsonEnvelope(opts: {
 	if (opts.count !== undefined) envelope.count = opts.count;
 	if (opts.error) envelope.error = opts.error;
 	envelope.data = opts.data;
+
+	// If the platform flagged this as an unclaimed Agent Mode account, surface
+	// the notice inside the JSON envelope so an agent consuming the output
+	// sees it without needing to inspect HTTP headers.
+	// eslint-disable-next-line @typescript-eslint/no-require-imports
+	const { takeNotice } = require("./state.js");
+	const notice = takeNotice();
+	if (notice) envelope.mem0_notice = notice;
+
 	console.log(JSON.stringify(envelope, null, 2));
 }
 
@@ -356,6 +366,12 @@ export function formatAgentEnvelope(opts: {
 	}
 	if (opts.count !== undefined) envelope.count = opts.count;
 	envelope.data = sanitizeAgentData(opts.command, opts.data);
+
+	// Surface the unclaimed-Agent-Mode notice (if any) in the envelope so an
+	// agent reading the JSON output sees it without inspecting HTTP headers.
+	const notice = takeNotice();
+	if (notice) envelope.mem0_notice = notice;
+
 	console.log(JSON.stringify(envelope, null, 2));
 }