test(e2e): cover classpath / referenced-libraries commands

[wenytang-ms]

Phase B: Classpath / Referenced Libraries coverage

Adds test/e2e-plans/java-dep-classpath.yaml exercising all four java.project.* referenced-library commands on an invisible (unmanaged-folder) project, plus the two distinct removeLibrary code paths.

Commands covered

Command	UI affordance	Plan cycle
java.project.refreshLibraries	Refresh inline icon on Referenced Libraries	1
java.project.addLibraries	+ inline icon -> simpleFileDialog jar pick	2
java.project.removeLibrary (include-removal)	command id (handler unchanged)	3
java.project.addLibraryFolders	command id -> Select Library Folders button	4
java.project.removeLibrary (exclude-add)	command id (handler unchanged)	5

Notable design decisions (documented inline in the YAML)

• Invisible projects do not auto-activate redhat.java -- bootstrap with open file src/App.java before waitForLanguageServer.
• Single-folder workspaces have no collapseWorkspaceRoot target -- use collapseSidebarSection invisible so the JAVA PROJECTS pane gets the vertical room virtualisation needs to render jar leaves.
• Jar leaves carry the resolved path in their accessible name -- drop exact: true on jar verifyTreeItem blocks (project root keeps it).
• Smoke-test driver swaps native showOpenDialog for simpleFileDialog -- drive the picker with fillQuickInput; folder pick additionally needs tryClickButton Select Library Folders because Enter on a folder navigates into it.
• removeLibrary is invoked via executeVSCodeCommand -- the inline minus icon hit-target is narrower than the wrapping <li class="action-item"> whose centre clickTreeItemAction targets, so the click consistently misses on jar-leaf rows. The command id bypasses the hit-target gap and exercises the same handler.
• Cycle 5 exercises the second removeLibrary branch -- after cycle 4 the folder glob re-attaches extra-a.jar; removing it again goes through the if (removedPaths.length === 0) path that appends to referencedLibraries.exclude.

Fixtures

• test/invisible/extraJars/extra-a.jar and extra-b.jar (added in a prior commit on this branch) enable the add-then-remove cycles without polluting the baseline lib/simple.jar.

Local verification

33/33 passed

Auto-discovered by the existing matrix in .github/workflows/e2eUI.yml via the discover-plans job -- no CI wiring needed.