Rename CLI and registry references to jpm

Updates tooling branding and configuration to use the jpm name and related defaults.

- Aligns CLI messaging and docs to reference jpm instead of previous name.
- Updates registry entry defaults (repository URL, destination path).
- Changes temporary working directory prefix used during fetch operations.
- Adds project SDK configuration entries for the IDE.
- Adjusts README usage instructions to match the renamed commands.

These changes keep tooling, docs, and runtime behavior consistent with the jpm namespace.

.idea/jeAddons.iml

@@ -4,6 +4,7 @@
     <content url="file://$MODULE_DIR$">
       <excludeFolder url="file://$MODULE_DIR$/.venv" />
     </content>
+    <orderEntry type="jdk" jdkName="uv (jpm)" jdkType="Python SDK" />
     <orderEntry type="sourceFolder" forTests="false" />
   </component>
 </module>

.idea/misc.xml

@@ -3,7 +3,7 @@
   <component name="Black">
     <option name="sdkName" value="uv (jeAddons)" />
   </component>
-  <component name="ProjectRootManager" version="2" />
+  <component name="ProjectRootManager" version="2" project-jdk-name="uv (jpm)" project-jdk-type="Python SDK" />
   <component name="RuffConfiguration">
     <option name="enabled" value="true" />
     <option name="inspections" value="false" />