Describe artifact retention as workflow-specific

Signed-off-by: Ralf W. Grosse-Kunstleve <rgrossekunst@nvidia.com>

Author: rwgk

CONTRIBUTING.md

@@ -442,7 +442,7 @@ for package/major names, local versus published bindings, and reuse details.
 
 - **Self-hosted runners**: Used for Linux builds and GPU testing (more resources, faster builds)
 - **GitHub-hosted runners**: Used for Windows builds and general tasks
-- **Artifact retention**: 30 days for GitHub Artifacts (wheels, docs, tests)
+- **Artifact retention**: Set per workflow for wheels, documentation, and test results
 - **Cache retention**: GitHub Cache for build dependencies and environments
 - **Security**: All commits must be signed, untrusted code blocked
 - **Parallel execution**: Matrix builds across Python versions and platforms

ci/ci-pipeline.mmd

@@ -42,7 +42,7 @@ flowchart TB
     subgraph ARTIFACTS["ARTIFACT STORAGE"]
         direction TB
         subgraph GITHUB_ARTIFACTS["GitHub Artifacts"]
-            GA1["Wheel files (.whl)<br/>Test artifacts<br/>Documentation<br/>(30-day retention)"]
+            GA1["Wheel files (.whl)<br/>Test artifacts<br/>Documentation<br/>(Workflow-specific retention)"]
         end
         subgraph GITHUB_CACHE["GitHub Cache"]
             GC1["Mini CTK cache"]