Add Workbench preview release stream

Add preview devVersion entries for both workbench and
workbench-session-init using the apple-blossom branch
codename. The channel value is used by bakery to resolve
the branch-specific dailies URL.

When the preview branch changes, update the channel value
here. Dispatches can also override at runtime via the
channel input on development.yml.

Author: bschwedler

bakery.yaml

@@ -65,6 +65,22 @@ images:
           - host: "ghcr.io"
             namespace: "posit-dev"
             repository: "workbench-preview"
+      - sourceType: stream
+        product: workbench
+        stream: preview
+        values:
+          channel: "apple-blossom"
+        os:
+          - name: Ubuntu 24.04
+            primary: true
+            platforms:
+              - linux/amd64
+              - linux/arm64
+          - name: Ubuntu 22.04
+        overrideRegistries:
+          - host: "ghcr.io"
+            namespace: "posit-dev"
+            repository: "workbench-preview"
     versions:
       - name: 2026.01.2+418.pro1
         subpath: '2026.01'
@@ -107,6 +123,21 @@ images:
           - host: "ghcr.io"
             namespace: "posit-dev"
             repository: "workbench-session-init-preview"
+      - sourceType: stream
+        product: workbench-session
+        stream: preview
+        values:
+          channel: "apple-blossom"
+        os:
+          - name: Ubuntu 24.04
+            primary: true
+            platforms:
+              - linux/amd64
+              - linux/arm64
+        overrideRegistries:
+          - host: "ghcr.io"
+            namespace: "posit-dev"
+            repository: "workbench-session-init-preview"
     versions:
       - name: 2026.01.2+418.pro1
         subpath: '2026.01'