fix(auth): honor SSL CA env vars across httpx + requests callsites

- hermes_cli/auth.py: add _default_verify() with macOS Homebrew certifi
  fallback (mirrors weixin 3a0ec1d93). Extend env var chain to include
  REQUESTS_CA_BUNDLE so one env var works across httpx + requests paths.
- agent/model_metadata.py: add _resolve_requests_verify() reading
  HERMES_CA_BUNDLE / REQUESTS_CA_BUNDLE / SSL_CERT_FILE in priority
  order. Apply explicit verify= to all 6 requests.get callsites.
- Tests: 18 new unit tests + autouse platform pin on existing
  TestResolveVerifyFallback to keep its "returns True" assertions
  platform-independent.

Empirically verified against self-signed HTTPS server: requests honors
REQUESTS_CA_BUNDLE only; httpx honors SSL_CERT_FILE only. Hermes now
honors all three everywhere.

Triggered by Discord reports — Nous OAuth SSL failure on macOS
Homebrew Python; custom provider self-signed cert ignored despite
REQUESTS_CA_BUNDLE set in env.

tests/hermes_cli/test_auth_ssl_macos.py

@@ -0,0 +1,115 @@
+"""Tests for hermes_cli.auth._default_verify platform-aware fallback.
+
+On macOS with Homebrew Python, the system OpenSSL cannot locate the
+system trust store, so we explicitly load certifi's bundle. On other
+platforms we defer to httpx's own default (which itself uses certifi).
+
+Most tests use monkeypatching — no real SSL handshakes. A handful use
+an openssl-generated self-signed cert via the `real_bundle_file`
+fixture because `ssl.create_default_context(cafile=...)` parses the
+bundle and refuses stubs.
+"""
+
+import os
+import shutil
+import ssl
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from hermes_cli.auth import _default_verify, _resolve_verify
+
+
+@pytest.fixture
+def real_bundle_file(tmp_path: Path) -> str:
+    """Return a path to a real openssl-generated self-signed cert.
+
+    Skips the test when the `openssl` binary isn't on PATH, so CI images
+    without it degrade gracefully instead of erroring out.
+    """
+    if shutil.which("openssl") is None:
+        pytest.skip("openssl binary not available")
+    cert = tmp_path / "ca.pem"
+    key = tmp_path / "key.pem"
+    result = subprocess.run(
+        [
+            "openssl", "req", "-x509", "-newkey", "rsa:2048",
+            "-keyout", str(key), "-out", str(cert),
+            "-sha256", "-days", "1", "-nodes",
+            "-subj", "/CN=test",
+        ],
+        capture_output=True,
+        timeout=10,
+    )
+    if result.returncode != 0:
+        pytest.skip(f"openssl failed: {result.stderr.decode('utf-8', 'ignore')[:200]}")
+    return str(cert)
+
+
+class TestDefaultVerify:
+    def test_returns_ssl_context_on_darwin(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "darwin")
+        result = _default_verify()
+        assert isinstance(result, ssl.SSLContext)
+
+    def test_returns_true_on_linux(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "linux")
+        assert _default_verify() is True
+
+    def test_returns_true_on_windows(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "win32")
+        assert _default_verify() is True
+
+    def test_darwin_falls_back_to_true_when_certifi_missing(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "darwin")
+
+        real_import = __import__
+
+        def fake_import(name, *args, **kwargs):
+            if name == "certifi":
+                raise ImportError("simulated missing certifi")
+            return real_import(name, *args, **kwargs)
+
+        monkeypatch.setattr("builtins.__import__", fake_import)
+        assert _default_verify() is True
+
+
+class TestResolveVerifyIntegration:
+    """_resolve_verify should defer to _default_verify in the no-CA path."""
+
+    def test_no_ca_uses_default_verify_on_darwin(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "darwin")
+        for var in ("HERMES_CA_BUNDLE", "SSL_CERT_FILE", "REQUESTS_CA_BUNDLE"):
+            monkeypatch.delenv(var, raising=False)
+        result = _resolve_verify()
+        assert isinstance(result, ssl.SSLContext)
+
+    def test_no_ca_uses_default_verify_on_linux(self, monkeypatch):
+        monkeypatch.setattr(sys, "platform", "linux")
+        for var in ("HERMES_CA_BUNDLE", "SSL_CERT_FILE", "REQUESTS_CA_BUNDLE"):
+            monkeypatch.delenv(var, raising=False)
+        assert _resolve_verify() is True
+
+    def test_requests_ca_bundle_respected(self, monkeypatch, real_bundle_file):
+        for var in ("HERMES_CA_BUNDLE", "SSL_CERT_FILE"):
+            monkeypatch.delenv(var, raising=False)
+        monkeypatch.setenv("REQUESTS_CA_BUNDLE", real_bundle_file)
+        result = _resolve_verify()
+        assert isinstance(result, ssl.SSLContext)
+
+    def test_missing_ca_path_falls_back_to_default_verify(self, monkeypatch, tmp_path):
+        monkeypatch.setattr(sys, "platform", "linux")
+        monkeypatch.setenv("HERMES_CA_BUNDLE", str(tmp_path / "missing.pem"))
+        for var in ("SSL_CERT_FILE", "REQUESTS_CA_BUNDLE"):
+            monkeypatch.delenv(var, raising=False)
+        assert _resolve_verify() is True
+
+    def test_insecure_wins_over_everything(self, monkeypatch, tmp_path):
+        bundle = tmp_path / "ca.pem"
+        bundle.write_text("stub")
+        monkeypatch.setenv("HERMES_CA_BUNDLE", str(bundle))
+        assert _resolve_verify(insecure=True) is False