[LalaLolLucky]

What changed and why

Follow-up to #153 (SAP ADT / ABAP). The first fix made getOpenEditors and the selection tools see ABAP editors, which report a file that has no disk path by its URI (semanticfs:/…). The tools that take a path then still assumed a local disk:

• openFile built a local file store from the path and failed (on Windows the : makes it an invalid path). It now opens such a file through the workspace (findFilesForLocationURI, which is what ADT's own editor expects, else the file system behind the URI), and finds the text editor of a multi-page editor so the line and selection still apply. Disk paths take the same route as before.
• openDiff / acceptDiff read and write by disk path. On Windows they threw an obscure path error; elsewhere the URI was taken for a new, relative file. They now refuse at once: "… is not a file on disk: the "semanticfs" file system keeps it, so this tool, which reads and writes files by path, cannot work on it. Use the editor it is open in instead."

What this does not do. It does not make ABAP sources editable through openDiff. After an accepted diff the CLI writes the file itself, by path, and there is no path to write to, so that needs a different mechanism (tools that read and change an open editor's document). This PR is only the hardening, so the failure is clear and openFile works. It references #153 and does not close it.

How was this tested?

• Unit tests: the new EditorParts helpers (a semanticfs:/http: URI is not a disk path; Windows drive letters, UNC paths, file: URIs, paths with a colon in a folder name and relative paths are; a URI with spaces is still not a disk path but gives no URI) and NonDiskDiffToolsTest (both tools refuse before touching the workbench). Compiled against the real Eclipse jars and run with the JUnit launcher: 23 tests pass (the existing EditorPartsTest and the new ones).
• Not exercised: openFile on a real semanticfs: file. It needs a running workbench and SAP ADT, which I don't have. The reporter on SAP ADT (ABAP) editors are invisible to getOpenEditors / getCurrentSelection / getWorkspaceFolders #153 offered to test a build against ADT.

Checklist

• I have not changed version numbers in MANIFEST.MF, feature.xml, or site.xml — the maintainer sets these on release.
• I have not added a CHANGELOG.md entry — the maintainer adds this on release.
• I have not hand-edited the generated p2 artifacts under com.anthropic.claudecode.eclipse.site/.
• If this touches claude-eclipse-core: I ran cargo test, and for any platform I can build and run on, rebuilt the native library and exercised it in a running Eclipse instance. (Not touched: Java only.)
• If this would need a native library for a platform I can't build and test myself, I've left that out and said so above rather than including an untested binary. (None needed.)