Fix colormap parsing against live GIBS API

Two bugs found via headless Claude CLI integration testing:

1. Colormap ID extraction: _detect_colormap returned the layer
   identifier as colormap_id, but GIBS layers often share colormaps
   under different filenames (e.g., AMSRU2_Sea_Ice_Concentration_12km
   -> colormap AMSR2_Sea_Ice_Concentration.xml). Now parses the actual
   filename from the metadata xlink:href.

2. Entries wrapper: GIBS v1.3 colormap XML nests ColorMapEntry elements
   inside an <Entries> wrapper. The parser only searched direct children
   of <ColorMap>, finding zero entries from live data. Now checks
   Entries/ColorMapEntry first, falling back to direct children.

Updated test fixture to use the real <Entries> wrapper structure.

src/mcgibs/capabilities.py

@@ -117,25 +117,44 @@ def _parse_bbox(layer_el: ET.Element) -> BBox | None:
     return BBox(west=west, south=south, east=east, north=north)
 
 
+def _extract_colormap_id_from_href(href: str) -> str | None:
+    """Extract the colormap identifier from a GIBS colormap URL.
+
+    GIBS metadata hrefs look like:
+      https://gibs.earthdata.nasa.gov/colormaps/v1.3/AMSR2_Sea_Ice_Concentration.xml
+
+    Multiple resolution layers often share a single colormap file, so the
+    colormap filename may differ from the layer identifier.
+    """
+    if not href:
+        return None
+    filename = href.rstrip("/").rsplit("/", 1)[-1]
+    if filename.endswith(".xml"):
+        return filename[:-4]
+    return None
+
+
 def _detect_colormap(layer_el: ET.Element, identifier: str) -> tuple[bool, str | None]:
     """Detect whether a layer has a colormap.
 
     GIBS layers with colormaps typically have:
+     - Metadata with xlink:role containing "colormap" (includes the URL)
      - A LegendURL element inside a Style
-     - Metadata with xlink:role containing "colormap"
 
-    Returns (has_colormap, colormap_id).
+    Returns (has_colormap, colormap_id).  The colormap_id is extracted from
+    the metadata href when available, falling back to the layer identifier.
     """
-    # Check for LegendURL in any Style
+    # Check metadata first — the href carries the actual colormap filename
-    for style in _findall(layer_el, "Style", _WMTS_URI):
-        if _find(style, "LegendURL", _WMTS_URI) is not None:
-            return True, identifier
-
-    # Check metadata for colormap hints
     for meta in _findall(layer_el, "Metadata", _OWS_URI):
         role = meta.get(f"{{{_XLINK_URI}}}role", "")
         href = meta.get(f"{{{_XLINK_URI}}}href", "")
         if "colormap" in role.lower() or "colormap" in href.lower():
+            colormap_id = _extract_colormap_id_from_href(href) or identifier
+            return True, colormap_id
+
+    # Fallback: check for LegendURL in any Style
+    for style in _findall(layer_el, "Style", _WMTS_URI):
+        if _find(style, "LegendURL", _WMTS_URI) is not None:
             return True, identifier
 
     return False, None

src/mcgibs/colormaps.py

@@ -209,9 +209,13 @@ def parse_colormap(xml_text: str) -> ColorMapSet:
         title = cm_elem.get("title", "")
         units = cm_elem.get("units", "")
 
-        # Parse entries
+        # Parse entries — GIBS v1.3 wraps them in <Entries>, but some
+        # documents have <ColorMapEntry> as direct children of <ColorMap>.
         entries: list[ColorMapEntry] = []
-        for entry_elem in cm_elem.findall("ColorMapEntry"):
+        entry_elements = cm_elem.findall("Entries/ColorMapEntry")
+        if not entry_elements:
+            entry_elements = cm_elem.findall("ColorMapEntry")
+        for entry_elem in entry_elements:
             rgb_raw = entry_elem.get("rgb", "0,0,0")
             entries.append(
                 ColorMapEntry(

tests/fixtures/colormap_sample.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <ColorMaps xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <ColorMap title="Surface Air Temperature" units="K">
+    <Entries>
       <ColorMapEntry rgb="227,245,255" transparent="false" sourceValue="[0,1)" value="[-INF,200.0)" ref="1"/>
       <ColorMapEntry rgb="204,234,252" transparent="false" sourceValue="[1,2)" value="[200.0,210.0)" ref="2"/>
       <ColorMapEntry rgb="150,200,230" transparent="false" sourceValue="[2,3)" value="[210.0,220.0)" ref="3"/>
@@ -15,6 +16,7 @@
       <ColorMapEntry rgb="220,50,30" transparent="false" sourceValue="[11,12)" value="[300.0,310.0)" ref="12"/>
       <ColorMapEntry rgb="180,20,50" transparent="false" sourceValue="[12,13)" value="[310.0,320.0)" ref="13"/>
       <ColorMapEntry rgb="251,3,207" transparent="false" sourceValue="[13,14)" value="[320.0,+INF)" ref="14"/>
+    </Entries>
     <Legend type="continuous">
       <LegendEntry rgb="227,245,255" tooltip="&lt; 200 K" id="1"/>
       <LegendEntry rgb="204,234,252" tooltip="200 - 210 K" id="2" showTick="true" showLabel="true"/>
@@ -24,7 +26,9 @@
     </Legend>
   </ColorMap>
   <ColorMap>
+    <Entries>
       <ColorMapEntry rgb="0,0,0" transparent="true" sourceValue="-9999" nodata="true" label="Missing Data"/>
+    </Entries>
     <Legend type="classification">
       <LegendEntry rgb="0,0,0" tooltip="Missing Data" id="1"/>
     </Legend>