feat(cli): Agent Mode bootstrap + claim flow (Python)

New behavior on `mem0 init`:
  - With no `--email`/`--api-key` AND a positive agent signal (`--agent`,
    global `--json`/`--agent`, or one of the recognized agent env vars
    CLAUDECODE / CURSOR_AGENT / CODEX_CLI / CLINE / CONTINUE / AIDER /
    GOOSE / WINDSURF), bootstrap an unattended Agent Mode account via
    POST /api/v1/auth/agent_mode/. No email, no OTP, no dashboard.
  - With `--email <addr>` AND an existing config that has agent_mode=true,
    run the claim device-flow against the existing key instead of minting
    a fresh one. The raw API key never leaves the device; backend confirms
    claim via the existing CLILoginRequest poll path. Config flips
    agent_mode=false and stamps claimed_at on success.
  - Bare `mem0 init` with no signal + no TTY still errors out — auto-bootstrap
    requires a positive agent signal to avoid surprising pipe-using humans.

New flags:
  --agent   Force unattended Agent Mode bootstrap.
  --source  Channel attribution string for signup_source PostHog property.

Config schema extensions on PlatformConfig:
  agent_mode, created_via, claimed_at, default_user_id.

Telemetry (M1-M6 from the growth doc):
  - cli.init: mode (agent|email|api_key|existing_key), agent_caller,
    signup_source, claimed_agent_mode (bool when --email claims an
    existing agent-mode config).
  - All cli.* events: agent_mode reflects config.platform.agent_mode (the
    bootstrap flag), not the output-format flag — per the growth-doc spec.

cli/python/src/mem0_cli/config.py

@@ -28,6 +28,11 @@ class PlatformConfig:
     api_key: str = ""
     base_url: str = DEFAULT_BASE_URL
     user_email: str = ""
+    # Agent Mode (unclaimed-shadow signup)
+    agent_mode: bool = False  # True while the key is an unclaimed agent-mode key
+    created_via: str = ""  # "agent_mode" | "email" | "api_key" | "existing_key"
+    claimed_at: str = ""  # ISO timestamp once the agent has been claimed by a human
+    default_user_id: str = ""  # `user_<slug>` returned by bootstrap; used as auto-default
 
 
 @dataclass
@@ -83,6 +88,10 @@ def load_config() -> Mem0Config:
         config.platform.api_key = plat.get("api_key", "")
         config.platform.base_url = plat.get("base_url", DEFAULT_BASE_URL)
         config.platform.user_email = plat.get("user_email", "")
+        config.platform.agent_mode = bool(plat.get("agent_mode", False))
+        config.platform.created_via = plat.get("created_via", "")
+        config.platform.claimed_at = plat.get("claimed_at", "")
+        config.platform.default_user_id = plat.get("default_user_id", "")
 
         defaults = data.get("defaults", {})
         config.defaults.user_id = defaults.get("user_id", "")
@@ -136,6 +145,10 @@ def save_config(config: Mem0Config) -> None:
             "api_key": config.platform.api_key,
             "base_url": config.platform.base_url,
             "user_email": config.platform.user_email,
+            "agent_mode": config.platform.agent_mode,
+            "created_via": config.platform.created_via,
+            "claimed_at": config.platform.claimed_at,
+            "default_user_id": config.platform.default_user_id,
         },
         "telemetry": {
             "anonymous_id": config.telemetry.anonymous_id,