feat(agenda): refresh the render cache on a timer, without the daemon

The surface reading this has to stay correct while Emacs is down, and
emacsclient is exactly the thing that cannot. So the writer is a batch
Emacs and a user timer runs it every five minutes.

- scripts/agenda-render-cache writes the cache from a batch Emacs. It
  resolves the agenda file list through the config's own resolver rather
  than restating it, so adding a calendar source stays a one-place change.
- The timer uses OnCalendar so Persistent actually applies. On a monotonic
  schedule it is silently ignored, and a machine that slept would come back
  to a stale file with nothing to trigger a catch-up.
- The window is now three days, yesterday through tomorrow. A consumer
  drawing a rolling window centred on now has nothing to draw for the part
  of its span outside today, which late in the evening is half the surface.

The keyword list moved to user-constants, where a batch Emacs can reach it
without this config's package dependencies. Without it org did not
recognise DOING or VERIFY, so it stopped parsing those headlines as tasks
at all: the keyword and priority cookie stayed glued to the front of every
title and each row reported no keyword and not-done. The file parsed
cleanly and was wrong, which is the failure worth guarding.

The bats tests run against a fixture and this checkout, not the machine's
real agenda and installed config. Asserting over live data let the same
suite pass on a day that happened to have no keyworded entries.

1 files changed, 15 insertions, 5 deletions

diff --git a/modules/agenda-query.el b/modules/agenda-query.el
index 5a185076..c98b7fb7 100644
--- a/modules/agenda-query.el
+++ b/modules/agenda-query.el
@@ -575,18 +575,28 @@ entry spans its day and a point event has zero width.  See
     json))
 
 (defun cj/agenda-render-cache-update ()
-  "Write today's agenda to `cj/agenda-render-cache-file' for the renderer.
+  "Write the agenda around today to `cj/agenda-render-cache-file'.
 
-The window is the whole local day, midnight to day close, so it is 23 or 25
-hours long on a DST changeover rather than a flat 24.  Returns the path.
+The window is three whole local days: yesterday's midnight through tomorrow's
+day close.  A consumer drawing a rolling window centred on now needs entries
+from either side of midnight, and a single calendar day leaves it with nothing
+to draw for the part of its span that falls outside today -- half the surface,
+late in the evening.  Three days covers any rolling span up to a full day
+either way, and the consumer filters to what it actually draws.
+
+Day boundaries are computed rather than assumed, so the span is 71, 72 or 73
+hours across a DST changeover rather than a flat 72.  Returns the path.
 
 Safe to call repeatedly and from a timer: it only reads org files, creates the
 cache directory if needed, and replaces the file by rename, so a reader on its
 own schedule never sees a partial write."
   (interactive)
   (let* ((d (decode-time (time-convert nil 'integer)))
-         (start (cj/--agenda-query-epoch 0 0 0 (nth 3 d) (nth 4 d) (nth 5 d)))
-         (end (cj/--agenda-query-day-close (nth 3 d) (nth 4 d) (nth 5 d))))
+         (day (nth 3 d)) (month (nth 4 d)) (year (nth 5 d))
+         ;; Out-of-range day fields normalize, so day 0 is last month's last
+         ;; day and day+1 rolls the month or year without special cases.
+         (start (cj/--agenda-query-epoch 0 0 0 (1- day) month year))
+         (end (cj/--agenda-query-day-close (1+ day) month year)))
     (make-directory (file-name-directory cj/agenda-render-cache-file) t)
     (cj/agenda-render-json start end cj/agenda-render-cache-file)
     (when (called-interactively-p 'interactive)