refactor: dedupe presenters, group defcustoms, and fill in docstrings

A cleanup pass over org-drill internals, squashed from the refactor/wave3-cleanup branch. No behavior change. Each step kept the existing tests green and added its own.

I shared two duplicated helpers across the language card getters: org-drill--read-property-string and org-drill--face-from-alist.

I factored the cloze body-scan out of the two multicloze presenters into org-drill--cloze-body-bounds, org-drill--count-cloze-matches, and org-drill--hide-cloze-by-index, so each presenter just picks which indices to hide.

I pulled the presenter resolution and the four-way result classification out of org-drill-entry-f into org-drill--resolve-presenter and org-drill--classify-presentation-result, untangling the pivot of every drill iteration.

I split the 37 defcustoms (and the three cloze faces) into four customize sub-groups (display, algorithm, session, leech) so customize-group org-drill is navigable. There's no leitner group because the Leitner settings are defvars.

I documented the 22 defuns that had no docstring, rewrote the corrupted org-drill-presentation-prompt-in-mini-buffer docstring, and switched eleven docstrings to the imperative "Return" (issue #2).

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/test-org-drill-explain-and-language-cards.el b/tests/test-org-drill-explain-and-language-cards.el
index 301705d..9454a0d 100644
--- a/tests/test-org-drill-explain-and-language-cards.el
+++ b/tests/test-org-drill-explain-and-language-cards.el
@@ -171,6 +171,34 @@ on whether the buffer ends with a newline."
            (face (get-text-property 0 'face (nth 0 info))))
       (should (equal "red" (plist-get face :foreground))))))
 
+;;;; org-drill--read-property-string
+
+(ert-deftest test-org-drill-read-property-string-strips-one-read ()
+  "A Lisp-readable property string is read down to its datum."
+  (should (equal "hablar" (org-drill--read-property-string "\"hablar\""))))
+
+(ert-deftest test-org-drill-read-property-string-nil-is-nil ()
+  "A nil property (absent) returns nil rather than erroring."
+  (should (null (org-drill--read-property-string nil))))
+
+;;;; org-drill--face-from-alist
+
+(ert-deftest test-org-drill-face-from-alist-hit-returns-colour ()
+  "A key present in the alist returns its mapped colour."
+  (should (equal "tomato"
+                 (org-drill--face-from-alist "present" org-drill-verb-tense-alist "x"))))
+
+(ert-deftest test-org-drill-face-from-alist-is-case-insensitive ()
+  "Lookup ignores case, matching the assoc-string call sites."
+  (should (equal "tomato"
+                 (org-drill--face-from-alist "PRESENT" org-drill-verb-tense-alist "x"))))
+
+(ert-deftest test-org-drill-face-from-alist-miss-returns-default ()
+  "A key absent from the alist falls back to the supplied default."
+  (should (equal "fallback"
+                 (org-drill--face-from-alist "no-such-tense"
+                                             org-drill-verb-tense-alist "fallback"))))
+
 (provide 'test-org-drill-explain-and-language-cards)
 
 ;;; test-org-drill-explain-and-language-cards.el ends here