fix(cron-recipes): pre-release hardening — honest cadences, strict slot names, surface-aware UX

Review fixes for the Cron Recipes stack before release:

- hydration-move: */90 in the cron minute field silently wraps to hourly
  (croniter-verified) — 90/120-minute options never fired at their stated
  cadence. Replaced with an hour-field step (0 9-17/2 * * 1-5) and an
  interval_hours slot whose options (1/2/3h) all fire as labeled.
- fill_recipe: reject unknown slot names. A typo'd 'tiem=07:15' used to
  silently create the job at the 08:00 default; now it 422s on the dashboard
  form and errors on the slash/deep-link paths with the valid slot list.
- deliver slot: non-strict enum (options are suggestions, scheduler
  validates downstream) so slack/whatsapp/etc. users aren't locked out;
  GET /api/cron/recipes rewrites its options from cron_delivery_targets()
  so the dashboard form only offers configured platforms; help text no
  longer claims dashboard-created jobs deliver to 'the chat you set this
  up from' (the endpoint strips origin — they go to the home channel).
- gateway: success/accept messages no longer point at /cron (cli_only);
  surface-aware hint instead. Conversational fill now sends the
  'Setting up X — I'll ask you a couple of things…' ack before the agent
  turn, matching the CLI experience.
- important-mail catalog entry: reference the urgency classifier by module
  path (python3 -m cron.scripts.classify_items) instead of baking an
  absolute host path into the job prompt — stale after relocation and
  nonexistent on remote terminal backends. cron/scripts is now a real
  package and ships in the wheel (pyproject packages.find).
- export_recipe: interval schedules round-trip again — parse_schedule
  stores 'minutes' but the renderer only read 'seconds', so every interval
  job exported as the silent '0 9 * * *' fallback.
- skills_hub install: say so when a recipe suggestion is dropped
  (latched dedup or pending cap) instead of printing nothing.

Targeted tests: 58 cron/recipe + 261 web_server pass; E2E-validated all
14 recipes fill+parse, hydration cadences via croniter, typo rejection on
slash + endpoint paths, surface-aware hints, and interval export round-trip.

tools/recipes.py

@@ -307,11 +307,19 @@ def _schedule_to_string(schedule: Any) -> str:
         kind = schedule.get("kind")
         if kind == "cron" and schedule.get("expr"):
             return str(schedule["expr"])
-        if kind == "interval" and schedule.get("seconds"):
-            secs = int(schedule["seconds"])
-            if secs % 3600 == 0:
-                return f"every {secs // 3600}h"
-            if secs % 60 == 0:
-                return f"every {secs // 60}m"
-            return f"every {secs}s"
+        if kind == "interval":
+            # parse_schedule stores interval periods as "minutes"; tolerate a
+            # legacy/foreign "seconds" form too.
+            if schedule.get("minutes"):
+                mins = int(schedule["minutes"])
+                if mins % 60 == 0:
+                    return f"every {mins // 60}h"
+                return f"every {mins}m"
+            if schedule.get("seconds"):
+                secs = int(schedule["seconds"])
+                if secs % 3600 == 0:
+                    return f"every {secs // 3600}h"
+                if secs % 60 == 0:
+                    return f"every {secs // 60}m"
+                return f"every {secs}s"
     return "0 9 * * *"  # safe daily fallback