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/backend/platform.ts

@@ -3,7 +3,7 @@
  */
 
 import type { PlatformConfig } from "../config.js";
-import { isAgentMode } from "../state.js";
+import { captureNotice, isAgentMode } from "../state.js";
 import { CLI_VERSION } from "../version.js";
 import {
 	APIError,
@@ -90,7 +90,39 @@ export class PlatformBackend implements Backend {
 		if (resp.status === 204) {
 			return {};
 		}
-		return resp.json();
+
+		const data = await resp.json();
+
+		// Pull the unclaimed-Agent-Mode notice out of the body (or the header
+		// fallback for endpoints returning non-dict / non-dict-leading payloads)
+		// and stash for end-of-command surfacing.
+		let notice: string | null = null;
+		if (
+			data &&
+			typeof data === "object" &&
+			!Array.isArray(data) &&
+			"mem0_notice" in data
+		) {
+			notice = (data as Record<string, unknown>).mem0_notice as string;
+			// biome-ignore lint/performance/noDelete: intentional strip so downstream consumers don't see duplicate notice
+			delete (data as Record<string, unknown>).mem0_notice;
+		} else if (
+			Array.isArray(data) &&
+			data.length > 0 &&
+			typeof data[0] === "object" &&
+			data[0] !== null &&
+			"mem0_notice" in data[0]
+		) {
+			notice = (data[0] as Record<string, unknown>).mem0_notice as string;
+			// biome-ignore lint/performance/noDelete: see above.
+			delete (data[0] as Record<string, unknown>).mem0_notice;
+		}
+		if (!notice) {
+			notice = resp.headers.get("X-Mem0-Notice-Message") ?? null;
+		}
+		captureNotice(notice);
+
+		return data;
 	}
 
 	async add(