fix(calendar-sync): run the sync from a timer instead of the agenda hook

The hourly timer armed itself from org-agenda-mode-hook, so a session where
I never opened the agenda never synced at all. After a reboot that is every
session until the first agenda call. I found it with all three calendar
files still frozen at the pre-reboot write, five hours stale.

The deferral had a real reason. Feed URLs behind :secret-host live in
authinfo.gpg, and starting at load would prompt for a passphrase on a cold
gpg-agent. The cost was worse than what it bought.

A user timer owns the schedule now, every ten minutes.
calendar-sync-auto-start defaults to nil so the editor no longer arms its
own. scripts/calendar-sync-run is the batch entry point, and it blocks
until every calendar leaves the syncing state. The pipeline is asynchronous
end to end, so a batch Emacs that returns early exits zero having written
nothing.

Installing it on a machine that resolves its feeds through :secret-host
surfaced two bugs the inline-url machine could never show:

- cj/auth-source-secret-value called auth-source-search behind nothing but
  a declare-function, which quiets the compiler and loads nothing. An
  interactive Emacs always has auth-source in by the time anyone calls, so
  the omission stayed invisible until a batch -Q sync died on a void
  function. The require is guarded on fboundp. An unconditional one reloads
  auth-source over whatever is already there, which replaced a caller's
  stubbed search mid-call and sent an existing test out to the real
  authinfo.

- A synchronous failure in one calendar aborted the whole loop. The async
  callbacks record their own failures, but they never run when the error
  lands before a process starts. Resolving a :secret-host feed signals
  outright on a cold agent. Failures are contained per calendar now, so one
  bad feed no longer costs the other two.

A failed row prints the reason it recorded. Batch Emacs discards the
*Messages* buffer the interactive path logs to, so without it the journal
shows only "error", with no way to tell a cold agent from a revoked token.

1 files changed, 18 insertions, 0 deletions

diff --git a/systemd/calendar-sync.timer b/systemd/calendar-sync.timer
new file mode 100644
index 00000000..71278f20
--- /dev/null
+++ b/systemd/calendar-sync.timer
@@ -0,0 +1,18 @@
+[Unit]
+Description=Sync calendars into org every 10 minutes
+
+[Timer]
+# OnCalendar rather than OnUnitActiveSec, because Persistent= only has an
+# effect on calendar timers (systemd.timer(5)). A monotonic schedule silently
+# ignores it, so a machine that slept through several intervals would come
+# back to stale calendar files with nothing to trigger a catch-up.
+OnCalendar=*:0/10
+Persistent=true
+# A cold boot should not wait for the next wall-clock slot. This is the case
+# the whole change exists for: before the timer, a reboot meant no calendar
+# sync at all until the agenda happened to be opened.
+OnBootSec=2min
+AccuracySec=30s
+
+[Install]
+WantedBy=timers.target