feat(agent): make API retry count configurable via agent.api_max_retries (#14730)

Closes #11616.

The agent's API retry loop hardcoded max_retries = 3, so users with
fallback providers on flaky primaries burned through ~3 × provider
timeout (e.g. 3 × 180s = 9 minutes) before their fallback chain got a
chance to kick in.

Expose a new config key:

    agent:
      api_max_retries: 3  # default unchanged

Set it to 1 for fast failover when you have fallback providers, or
raise it if you prefer longer tolerance on a single provider. Values
< 1 are clamped to 1 (single attempt, no retry); non-integer values
fall back to the default.

This wraps the Hermes-level retry loop only — the OpenAI SDK's own
low-level retries (max_retries=2 default) still run beneath this for
transient network errors.

Changes:
- hermes_cli/config.py: add agent.api_max_retries default 3 with comment.
- run_agent.py: read self._api_max_retries in AIAgent.__init__; replace
  hardcoded max_retries = 3 in the retry loop with self._api_max_retries.
- cli-config.yaml.example: documented example entry.
- hermes_cli/tips.py: discoverable tip line.
- tests/run_agent/test_api_max_retries_config.py: 4 tests covering
  default, override, clamp-to-one, and invalid-value fallback.

tests/run_agent/test_api_max_retries_config.py

@@ -0,0 +1,65 @@
+"""Tests for agent.api_max_retries config surface.
+
+Closes #11616 — make the hardcoded ``max_retries = 3`` in the agent's API
+retry loop user-configurable so fallback-provider setups can fail over
+faster on flaky primaries instead of burning ~3x180s on the same stall.
+"""
+from unittest.mock import MagicMock, patch
+
+from run_agent import AIAgent
+
+
+def _make_agent(api_max_retries=None):
+    """Build an AIAgent with a mocked config.load_config that returns a
+    config tree containing the given agent.api_max_retries (or default)."""
+    cfg = {"agent": {}}
+    if api_max_retries is not None:
+        cfg["agent"]["api_max_retries"] = api_max_retries
+
+    with patch("run_agent.OpenAI"), \
+         patch("hermes_cli.config.load_config", return_value=cfg):
+        return AIAgent(
+            api_key="test-key",
+            base_url="https://openrouter.ai/api/v1",
+            model="test/model",
+            quiet_mode=True,
+            skip_context_files=True,
+            skip_memory=True,
+        )
+
+
+def test_default_api_max_retries_is_three():
+    """No config override → legacy default of 3 retries preserved."""
+    agent = _make_agent()
+    assert agent._api_max_retries == 3
+
+
+def test_api_max_retries_honors_config_override():
+    """Setting agent.api_max_retries in config propagates to the agent."""
+    agent = _make_agent(api_max_retries=1)
+    assert agent._api_max_retries == 1
+
+    agent2 = _make_agent(api_max_retries=5)
+    assert agent2._api_max_retries == 5
+
+
+def test_api_max_retries_clamps_below_one_to_one():
+    """0 or negative values would disable the retry loop entirely
+    (the ``while retry_count < max_retries`` guard would never execute),
+    so clamp to 1 = single attempt, no retry."""
+    agent = _make_agent(api_max_retries=0)
+    assert agent._api_max_retries == 1
+
+    agent2 = _make_agent(api_max_retries=-3)
+    assert agent2._api_max_retries == 1
+
+
+def test_api_max_retries_falls_back_on_invalid_value():
+    """Garbage values in config don't crash agent init — fall back to 3."""
+    agent = _make_agent(api_max_retries="not-a-number")
+    assert agent._api_max_retries == 3
+
+    agent2 = _make_agent(api_max_retries=None)
+    # None with dict.get default fires → default(3), then int(None) raises
+    # TypeError → except branch sets to 3.
+    assert agent2._api_max_retries == 3