Show source jar file for the currently opened class tab

**Is your feature request related to a problem? Please describe.**
When a workspace has multiple loaded jars (either as the primary resource, or as embedded resources inside a supporting directory resource), there's no straightforward way in the UI to tell which jar file a given open tab's
class actually came from. This becomes especially painful with workspaces containing a lot of jars.

Currently the only way I found to get this info was writing a custom script that walks the PathNode parent chain via NavigationManager to find the nearest ResourcePathNode, and cross-references the active tab via DockContainerLeaf#getSelectedDockable().

**Describe the solution you'd like**
Surface the source resource directly in the UI for the currently open/active tab, for example:
- Show the containing jar/file name in the tab's tooltip
- Show it in a status bar at the bottom of the window
- Add a "Reveal in tree" / "Locate resource" context menu action on the tab, which expands the workspace tree to the resource that contains the class

**Describe alternatives you've considered**
Manually switching between resources in the workspace tree dropdown and searching for the class visually — not practical with a large number of jars.

**Additional context**
Happy to test this against a workspace with a lot of jars if useful for verifying the fix works with deeply nested/mbedded resources (directory resource containing multiple jar resources).

Start with the active tab lookup through DockContainerLeaf#getSelectedDockable() and trace its class through the PathNode parent chain via NavigationManager to the nearest ResourcePathNode. Determine which UI surface best exposes the containing jar or file, including nested resources; done means the active class tab clearly identifies its source in workspaces with multiple and embedded jars.

Written by the indexing model from the issue text.