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, 54 insertions, 0 deletions

diff --git a/tests/test-system-lib--completion-file-annotator.el b/tests/test-system-lib--completion-file-annotator.el
new file mode 100644
index 000000000..9e1f4aa4a
--- /dev/null
+++ b/tests/test-system-lib--completion-file-annotator.el
@@ -0,0 +1,54 @@
+;;; test-system-lib--completion-file-annotator.el --- Tests for cj/completion-file-annotator -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for `cj/completion-file-annotator', the annotation-function
+;; factory used to annotate file-basename completion pickers with size and
+;; modification date.
+
+;;; Code:
+
+(require 'ert)
+(require 'system-lib)
+
+(ert-deftest test-system-lib-completion-file-annotator-normal-file-shows-size-and-date ()
+  "Normal: a regular file is annotated with a size and an ISO date."
+  (let ((file (make-temp-file "cfa-test-" nil ".txt" "hello world")))
+    (unwind-protect
+        (let* ((annotate (cj/completion-file-annotator
+                          (lambda (_cand) file)))
+               (result (funcall annotate "anything")))
+          (should (stringp result))
+          ;; file-size-human-readable of 11 bytes is "11"
+          (should (string-match-p "11" result))
+          ;; ISO date for the file's mtime
+          (should (string-match-p
+                   (format-time-string "%Y-%m-%d"
+                                       (file-attribute-modification-time
+                                        (file-attributes file)))
+                   result)))
+      (delete-file file))))
+
+(ert-deftest test-system-lib-completion-file-annotator-boundary-directory-marked-dir ()
+  "Boundary: a directory candidate is annotated with the `dir' marker."
+  (let ((dir (make-temp-file "cfa-dir-" t)))
+    (unwind-protect
+        (let* ((annotate (cj/completion-file-annotator (lambda (_c) dir)))
+               (result (funcall annotate "d")))
+          (should (stringp result))
+          (should (string-match-p "dir" result)))
+      (delete-directory dir t))))
+
+(ert-deftest test-system-lib-completion-file-annotator-error-nil-path-returns-nil ()
+  "Error: a candidate whose path-resolver returns nil yields no annotation."
+  (let ((annotate (cj/completion-file-annotator (lambda (_c) nil))))
+    (should (null (funcall annotate "missing")))))
+
+(ert-deftest test-system-lib-completion-file-annotator-error-missing-file-returns-nil ()
+  "Error: a path that does not exist yields no annotation."
+  (let* ((path (expand-file-name "definitely-not-here-12345.txt"
+                                 temporary-file-directory))
+         (annotate (cj/completion-file-annotator (lambda (_c) path))))
+    (should (null (funcall annotate "gone")))))
+
+(provide 'test-system-lib--completion-file-annotator)
+;;; test-system-lib--completion-file-annotator.el ends here