Card: drop the bare viewer link, document browser visualization

README.md

@@ -74,6 +74,8 @@ DICOM series in the NCI Imaging Data Commons; it does not contain pixel data.**
 Research Data Commons repository of publicly available cancer imaging data,
 co-located with analysis tools in the cloud. To explore it interactively
 instead, use the [IDC portal](https://portal.imaging.datacommons.cancer.gov/explore/).
+Without downloading anything, any image in IDC can be
+[viewed in the browser](https://learn.canceridc.dev/portal/visualization).
 To query IDC in plain language, point an AI assistant at its
 [agent interfaces](https://learn.canceridc.dev/ai-assistants/agents) --
 a hosted MCP server, an agent skill, and a REST API over the same metadata.
@@ -127,13 +129,18 @@ Downloads come directly from IDC's public AWS and GCS buckets at no cost to you.
 What lands on disk is DICOM; read it with [pydicom](https://pydicom.github.io/)
 or [highdicom](https://highdicom.readthedocs.io/).
 
-To look at a series before downloading it, get a viewer link for it. This picks
-the right viewer for the modality -- OHIF for radiology, slim for microscopy:
+Every series in this catalog can also be looked at without downloading
+anything. IDC streams the pixels to a zero-footprint browser viewer, and
+`get_viewer_URL` builds a link to any series you have selected:
 
 ```python
 print(client.get_viewer_URL(seriesInstanceUID=sel["SeriesInstanceUID"][0]))
 ```
 
+It picks the viewer that fits the data -- OHIF for radiology, slim for slide
+microscopy -- and opens the enclosing study with your series selected. Passing
+a segmentation, as above, brings it up overlaid on the images it segments.
+
 Query the catalog without downloading anything, using DuckDB:
 
 ```sql
@@ -325,7 +332,7 @@ and this card are ever written or removed by the publishing job.
 ## Links
 
 - [IDC portal](https://portal.imaging.datacommons.cancer.gov/explore/) -- browse the data and build cohorts interactively
-- [IDC viewer](https://viewer.imaging.datacommons.cancer.gov/) -- view images in the browser; get per-series links with `IDCClient.get_viewer_URL()`
+- [Visualizing IDC images](https://learn.canceridc.dev/portal/visualization) -- how the browser viewers work; get a link to any series with `IDCClient.get_viewer_URL()`
 - [IDC agent interfaces](https://learn.canceridc.dev/ai-assistants/agents) -- search IDC, size a cohort and get a download command by asking: hosted MCP server, agent skill, or REST API
 - [IDC documentation](https://learn.canceridc.dev/)
 - [`idc-index` Python package](https://github.com/ImagingDataCommons/idc-index) -- the download client (`pip install idc-index`)