agenda: Add header to agenda clock report table

* lisp/org-agenda.el (org-agenda-list): Add header to agenda clock
report table.

TINYCHANGE

doc/org-manual.org

@@ -9742,8 +9742,8 @@ the other commands, point needs to be in the desired line.
   variable ~org-agenda-start-with-clockreport-mode~.  By using
   a prefix argument when toggling this mode (i.e., {{{kbd(C-u R)}}}),
   the clock table does not show contributions from entries that are
-  hidden by agenda filtering[fn:99].  See also the variable
- ~org-clock-report-include-clocking-task~.
+  hidden by agenda filtering[fn:99].  See also the variables
+ ~org-clock-report-include-clocking-task~ and ~org-agenda-clock-report-header~.
 
 - {{{kbd(v c)}}} ::
 

etc/ORG-NEWS

@@ -140,6 +140,7 @@ introduced which will accept three new formats:
 Chmod-style permissions are based on the new variable
 ~org-babel-tangle-default-file-mode~.
 
+*** A new custom setting =org-agenda-clock-report-header= to add a header to org agenda clock report
 * Version 9.5
 
 ** Important announcements and breaking changes

lisp/org-agenda.el

@@ -1219,6 +1219,15 @@ For example, 9:30am would become 09:30 rather than  9:30."
   :version "24.1"
   :type 'boolean)
 
+(defcustom org-agenda-clock-report-header nil
+  "Header for org agenda clock report mode"
+  :group 'org-agenda
+  :type '(choice
+    (string :tag "Header")
+    (const :tag "No header" nil))
+  :safe #'stringp
+  :package-version '(Org . "9.6"))
+
 (defun org-agenda-time-of-day-to-ampm (time)
   "Convert TIME of a string like \"13:45\" to an AM/PM style time string."
   (let* ((hour-number (string-to-number (substring time 0 -3)))
@@ -4475,6 +4484,8 @@ items if they have an hour specification like [h]h:mm."
 	  (setq p (plist-put p :tend clocktable-end))
 	  (setq p (plist-put p :scope 'agenda))
 	  (setq tbl (apply #'org-clock-get-clocktable p))
+    (when org-agenda-clock-report-header
+      (insert (propertize org-agenda-clock-report-header 'face 'org-agenda-structure)))
 	  (insert tbl)))
       (goto-char (point-min))
       (or org-agenda-multi (org-agenda-fit-window-to-buffer))