[Repo Assist] fix: re-enable ImplementInterface tests by trimming FCS trailing whitespace (#1505)

* fix: re-enable ImplementInterface tests by trimming FCS trailing whitespace

FCS (since 43.7.200) emits trailing spaces on lines ending with '='
before a line break in generated interface stubs. This caused all
ImplementInterface tests to fail, so the entire test suite was wrapped
in ptestList (pending/skipped).

Fix: post-process the generated stub from FormatInterface to trim
trailing whitespace on each line.

Re-enable tests: change ptestList to testList so the 40 previously-
skipped tests now run and pass. Two remaining pending tests:
- 'cursor position' sub-list (still uses the disabled without-type-
  annotation fix path, pending FCS #14698)
- 'can implement setter when existing getter' (FCS 43.10.x does not
  detect inline getter 'member _.X with get () = val' as already
  implemented, causing both getter and setter to be regenerated;
  marked ptestCaseAsync pending investigation)

Partially addresses #1054.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* ci: trigger checks

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/FsAutoComplete/CodeFixes/ImplementInterface.fs

@@ -299,6 +299,13 @@ let fix (getParseResultsForFile: GetParseResultsForFile) (config: unit -> Config
                   entity
                   withTypeAnnotation
 
+              // FCS may emit trailing spaces on lines ending with `=` followed by a line break.
+              // Trim each line's trailing whitespace to produce clean output.
+              let stub =
+                stub.Split('\n')
+                |> Array.map (fun line -> line.TrimEnd([| ' '; '\t'; '\r' |]))
+                |> String.concat "\n"
+
               stub.TrimEnd(System.Environment.NewLine.ToCharArray())
 
             { Range = fcsPosToProtocolRange insertionData.InsertAt