feat(cron): routing intent — deliver=all fans out to every connected channel (#21495)

Adds one reserved token to the cron `deliver` field:

- `all` — expand to every platform with a configured home channel

Resolves at fire time, not create time, so a job created before Telegram
was wired up picks it up once `TELEGRAM_HOME_CHANNEL` is set. Composes
with existing targets: `origin,all`, `all,telegram:-100:17`.

Inspired by Vellum Assistant's reminder routing-intent system.

## Changes
- cron/scheduler.py: _expand_routing_tokens + integrate into _resolve_delivery_targets
- tools/cronjob_tools.py: schema description updated
- tests/cron/test_scheduler.py: TestRoutingIntents (5 cases)
- website/docs/user-guide/features/cron.md: docs + table rows

## Validation
- tests/cron/test_scheduler.py -k 'Routing or Deliver' → 57 passed

cron/scheduler.py

@@ -360,12 +360,52 @@ def _normalize_deliver_value(deliver) -> str:
     return str(deliver)
 
 
+# Routing intent tokens — resolved at fire time, not create time, so a
+# job created before Telegram was wired up will pick up Telegram once it
+# comes online.  ``all`` expands into the set of connected platforms
+# (those with a configured home chat_id) in _expand_routing_tokens.
+_ROUTING_TOKENS = frozenset({"all"})
+
+
+def _expand_routing_tokens(part: str) -> List[str]:
+    """Expand a routing-intent token to concrete platform names.
+
+    ``all`` expands to every platform in ``_iter_home_target_platforms()``
+    that has a configured home chat_id right now.  Unknown / non-token
+    values pass through unchanged as a single-element list, so the caller
+    can treat every token uniformly.
+    """
+    token = part.lower()
+    if token not in _ROUTING_TOKENS:
+        return [part]
+    expanded: List[str] = []
+    for platform_name in _iter_home_target_platforms():
+        if _get_home_target_chat_id(platform_name):
+            expanded.append(platform_name)
+    return expanded
+
+
 def _resolve_delivery_targets(job: dict) -> List[dict]:
-    """Resolve all concrete auto-delivery targets for a cron job (supports comma-separated deliver)."""
+    """Resolve all concrete auto-delivery targets for a cron job.
+
+    Accepts the legacy comma-separated ``deliver`` string plus the
+    ``all`` routing-intent token, which expands to every platform with
+    a configured home channel.  Tokens may be combined with explicit
+    targets: ``origin,all`` and ``all,telegram:-100:17`` both work.
+    Duplicate (platform, chat_id, thread_id) tuples are collapsed by the
+    existing dedup pass.
+    """
     deliver = _normalize_deliver_value(job.get("deliver", "local"))
     if deliver == "local":
         return []
-    parts = [p.strip() for p in deliver.split(",") if p.strip()]
+
+    raw_parts = [p.strip() for p in deliver.split(",") if p.strip()]
+
+    # Expand routing intents.
+    parts: List[str] = []
+    for raw in raw_parts:
+        parts.extend(_expand_routing_tokens(raw))
+
     seen = set()
     targets = []
     for part in parts: