feat(privacy): warn when LLM tier sends content to external API

4 files changed, 248 insertions, 0 deletions. 7 new tests (4 unit + 3 integration), all RED-first.

Per @milla-jovovich's question to @igorls during PR #1221 review: users
running `mempalace init` with an external LLM provider (Anthropic API,
OpenAI hosted, etc.) need a clear, explicit warning that their folder
content will be sent to the provider, that MemPalace doesn't control
how the provider logs/retains/uses that data, and how to opt out.
@igorls confirmed this should be a small follow-up PR scoped to the
warning itself, before the v3.3.4 tag.

This PR adds:

- `_endpoint_is_local(url)` helper in `mempalace/llm_client.py` —
  URL-based heuristic returning True if the hostname is on the user's
  machine or private network. Covers: localhost, 127.0.0.1, ::1,
  hostnames ending in .local (mDNS/Bonjour), IPv4 RFC1918 ranges
  (10/8, 172.16-31/12, 192.168/16), and IPv6 unique-local addresses
  (fc00::/7).

- `is_external_service` property on the `LLMProvider` base class.
  Subclasses inherit; the URL determines (no provider-specific
  hardcoding). This means: Ollama on localhost = local. LM Studio on
  LAN = local. Anthropic with default `https://api.anthropic.com` =
  external. A user proxying Anthropic through localhost (advanced
  setup) = local, no false-positive warning.

- One-line warning print in `cmd_init` after successful provider
  acquisition, gated on `is_external_service`:

      ⚠ {provider_name} is an EXTERNAL API. Your folder content will be
      sent to the provider during init. MemPalace does not control how
      the provider logs, retains, or uses your data. Pass --no-llm to
      keep init fully local.

  The warning fires AFTER `LLM enabled: ...` so users see both that
  the LLM is engaged AND the privacy implications of where it lives,
  before Pass 0 / entity detection actually runs.

LOCAL providers (Ollama on localhost, LM Studio on localhost or LAN,
llama.cpp on localhost, vLLM on localhost) DO NOT trigger the warning —
nothing leaves the user's machine/network in those configurations.

TDD: 7 tests added across 2 files.

Unit tests in `tests/test_llm_client.py` (4 tests, all RED-first):

1. test_ollama_provider_default_endpoint_is_local — pins that the
   default `http://localhost:11434` is classified local.
2. test_openai_compat_provider_localhost_endpoint_is_local — covers
   the LM Studio / llama.cpp / vLLM common case (localhost,
   127.0.0.1, and 192.168.x LAN).
3. test_openai_compat_provider_cloud_endpoint_is_external — pins
   that pointing openai-compat at https://api.openai.com (or any
   non-local URL) classifies as external.
4. test_anthropic_provider_default_endpoint_is_external — pins that
   AnthropicProvider's default endpoint is external (the dominant
   user-facing case for `--llm-provider anthropic`).

Integration tests in `tests/test_corpus_origin_integration.py` (3 tests,
RED-first; 1 was the critical RED — the other 2 passed by accident
since nothing printed "EXTERNAL API" before this PR):

5. test_init_prints_privacy_warning_when_provider_is_external —
   captures stdout from cmd_init with a mocked external provider,
   asserts the warning text contains "EXTERNAL API" + "--no-llm" +
   language about MemPalace not controlling provider behavior.
6. test_init_no_privacy_warning_when_provider_is_local — same flow
   with a mocked local provider, asserts the warning text does NOT
   appear.
7. test_init_no_privacy_warning_with_no_llm_flag — pins the --no-llm
   path: no provider acquisition attempted, no warning fires.

Tests: 1382 total mempalace tests pass. 2 pre-existing environmental
failures unrelated to this change (chromadb optional dep). Ruff check +
format both clean.

Backwards compatible: `is_external_service` is a new property; existing
callers don't reference it. The warning is a new print statement that
fires only when an external endpoint is acquired. The `--no-llm` opt-out
existed before this PR and continues to work identically.

Out of scope for follow-up (deliberately not in this PR per Igor's
"small PR" guidance): Tailscale CGNAT (100.64.0.0/10) treatment,
pre-init confirmation prompt, persistent privacy-mode config flag,
explicit cloud-provider name detection. Tracked for future iteration.

tests/test_llm_client.py

@@ -325,3 +325,56 @@ def test_anthropic_no_key_raises_on_classify(monkeypatch):
     p = AnthropicProvider(model="claude-haiku")
     with pytest.raises(LLMError, match="requires ANTHROPIC_API_KEY"):
         p.classify("s", "u")
+
+
+# ── is_external_service property (issue #24 — privacy warning support) ──
+#
+# `is_external_service` is True when this provider's endpoint sends data
+# off the user's machine/network. Used by mempalace init to print a
+# privacy warning before first run when an external API will receive
+# folder content. URL-based heuristic: localhost, 127.x, ::1, .local,
+# RFC1918 (10/8, 192.168/16, 172.16-31/12), and IPv6 ULA (fc/fd::) are
+# all treated as local. Everything else is treated as external.
+
+
+def test_ollama_provider_default_endpoint_is_local():
+    """OllamaProvider's default endpoint is http://localhost:11434, which
+    must be classified as local — no privacy warning fires for the
+    typical user running Ollama on their own machine."""
+    p = OllamaProvider(model="gemma4:e4b")
+    assert p.is_external_service is False, (
+        f"Default OllamaProvider endpoint must be local; got "
+        f"is_external_service={p.is_external_service} for endpoint={p.endpoint}"
+    )
+
+
+def test_openai_compat_provider_localhost_endpoint_is_local():
+    """LM Studio / llama.cpp server / vLLM commonly bind to localhost.
+    Those setups must NOT trigger the external-API warning."""
+    p = OpenAICompatProvider(model="any", endpoint="http://localhost:1234")
+    assert p.is_external_service is False
+    p_127 = OpenAICompatProvider(model="any", endpoint="http://127.0.0.1:8000")
+    assert p_127.is_external_service is False
+    p_lan = OpenAICompatProvider(model="any", endpoint="http://192.168.1.50:1234")
+    assert p_lan.is_external_service is False, "LAN (RFC1918) endpoints must be local"
+
+
+def test_openai_compat_provider_cloud_endpoint_is_external():
+    """A user pointing openai-compat at OpenAI's hosted API or any other
+    non-local endpoint MUST trigger the external warning."""
+    p = OpenAICompatProvider(model="gpt-4o", endpoint="https://api.openai.com")
+    assert p.is_external_service is True, (
+        f"https://api.openai.com must be classified external; got "
+        f"is_external_service={p.is_external_service}"
+    )
+
+
+def test_anthropic_provider_default_endpoint_is_external():
+    """AnthropicProvider's default endpoint is https://api.anthropic.com,
+    which is always external by definition. The privacy warning MUST
+    fire by default for users who pass --llm-provider anthropic."""
+    p = AnthropicProvider(model="claude-haiku-4-5", api_key="sk-test")
+    assert p.is_external_service is True, (
+        f"Default AnthropicProvider endpoint must be external; got "
+        f"is_external_service={p.is_external_service} for endpoint={p.endpoint}"
+    )