feat(completion): annotate the file-basename pickers with size and date

Eight completing-read pickers listed bare file basenames, so marginalia had no directory to resolve and couldn't annotate them. Add cj/completion-file-annotator to system-lib — an annotation-function factory that takes a candidate->path resolver and yields a size + modification-date suffix (or "dir" for directories, nil for missing files). Wire each picker through cj/completion-table-annotated with a per-site category and resolver: timer sounds, drill flashcards, Info files, the test-runner focus add/remove, vc clone dirs, hugo drafts, and agenda projects (the project's todo.org mtime). music-config's existing completion table gains the category and annotator inline, keeping its sort metadata.

The candidate strings and every return value are unchanged — this only adds completion metadata — so all downstream logic is untouched. The six modules that didn't already pull in system-lib now require it.

Tests: cj/completion-file-annotator gets Normal/Boundary/Error coverage (file, directory, nil path, missing file). Full suite green at 5394.

Claude-Session: https://claude.ai/code/session_014fyKMTTqLrZpL3rDF3dYc3

1 files changed, 21 insertions, 0 deletions

diff --git a/modules/system-lib.el b/modules/system-lib.el
index 8b954c6a9..f1049c021 100644
--- a/modules/system-lib.el
+++ b/modules/system-lib.el
@@ -187,6 +187,27 @@ for: marginalia falls back to the table's own annotation function."
                    (annotation-function . ,annotate))
       (complete-with-action action collection string predicate))))
 
+(defun cj/completion-file-annotator (candidate->path)
+  "Return an annotation function for completion candidates backed by files.
+CANDIDATE->PATH maps a candidate string to its absolute file path, or nil when
+the candidate has no backing file.  The returned function, suitable as a
+completion table's annotation function (see `cj/completion-table-annotated'),
+yields a suffix with the file size and modification date for a regular file,
+the marker \"dir\" plus the date for a directory, or nil when the path is nil
+or the file is missing -- so marginalia then shows no suffix for that
+candidate."
+  (lambda (cand)
+    (let ((path (funcall candidate->path cand)))
+      (when (and path (file-exists-p path))
+        (let* ((attrs (file-attributes path))
+               (dirp  (eq t (file-attribute-type attrs)))
+               (size  (if dirp "dir"
+                        (file-size-human-readable (file-attribute-size attrs))))
+               (date  (format-time-string
+                       "%Y-%m-%d"
+                       (file-attribute-modification-time attrs))))
+          (format "  %8s  %s" size date))))))
+
 (defun cj/format-region-with-program (program &rest args)
   "Replace the current buffer with PROGRAM ARGS run over its contents, via argv.
 Runs PROGRAM (with ARGS) on the whole buffer through `call-process-region'