fix(usage-window): keep an allowance whose reset is unknown

Greptile: "Unknown resets hide valid gauges". parse_gauges accepts a valid
allowance with an unknown reset, but _bp_window dropped the row because the
reset was not an int; with every reset unknown, build_nous_credits_snapshot
fell back to the dollar view and lost the window plan. The row now keeps
its percent with reset_at=None, which every renderer already shows as no
reset phrase (the same shape other providers' windows use).

agent/account_usage.py

@@ -202,13 +202,13 @@ def _nous_snapshot(windows: list, details: list, tail: list, *, source: str, pla
 
 
 def _bp_window(label: str, used_bp: Any, resets_at_ms: Any) -> Optional[AccountUsageWindow]:
-    """One usage-window gauge row from basis points + an epoch-ms reset; None when either is not an int."""
-    if isinstance(used_bp, bool) or not isinstance(used_bp, int) or isinstance(resets_at_ms, bool) or not isinstance(resets_at_ms, int):
+    """One usage-window gauge row from basis points + an epoch-ms reset (already bounded by
+    ``usage_gauges.parse_gauges``); None when the percent is not an int. An unknown reset keeps the row,
+    shown without a reset."""
+    if isinstance(used_bp, bool) or not isinstance(used_bp, int):
         return None
-    try:
-        reset_at = datetime.fromtimestamp(resets_at_ms / 1000, tz=UTC)
-    except (ValueError, OverflowError, OSError):
-        return None  # an implausible server stamp drops the row, never the whole /usage view
+    known = isinstance(resets_at_ms, int) and not isinstance(resets_at_ms, bool)
+    reset_at = datetime.fromtimestamp(resets_at_ms / 1000, tz=UTC) if known else None
     return AccountUsageWindow(label=label, used_percent=max(0.0, min(100.0, used_bp / BP_FULL * 100.0)),
                               reset_at=reset_at)
 

tests/agent/test_credits_usage_window.py

@@ -766,6 +766,19 @@ class TestUsageCommand:
                           "resets_at_ms": now + 3600_000}, *_gauges(100, 200, **kw)]
         assert next(w.label for w in account_usage.build_nous_credits_snapshot(info).windows) == "Next 5 hours"
 
+    def test_an_unknown_reset_keeps_the_allowance_row(self):
+        """A valid percent with no usable reset still shows as a window row (no reset phrase), never the
+        dollar view: the window plan's details stay on screen."""
+        from agent import account_usage
+        gauges = [{"id": "day", "scope": "all", "label": "Today", "used_bp": 4_200},
+                  {"id": "week", "scope": "all", "label": "This week", "used_bp": 1_000, "resets_at_ms": "soon"}]
+        info = SimpleNamespace(logged_in=True, paid_service_access=True, paid_service_access_info=None, subscription=None,
+                               usage_window=SimpleNamespace(gauges=gauges, paused_reason=None))
+        snap = account_usage.build_nous_credits_snapshot(info)
+        assert snap.usage_window and [(w.label, round(w.used_percent), w.reset_at) for w in snap.windows] == [
+            ("Today", 42, None), ("This week", 10, None)]
+        assert not any("resets" in line for line in account_usage.render_account_usage_lines(snap))
+
     def test_header_gauge_raises_stale_portal_percents(self, monkeypatch):
         from agent import account_usage
         monkeypatch.setattr("hermes_cli.nous_account.nous_portal_topup_url", lambda info: "https://portal/topup")