Docs: warn about the half-filled bucket, and say which node schedules

Say on the querying-chart page that a flow doing its own binning has to drop
the newest bucket, as the observability endpoints already do, and make plain
that `inject` is the scheduler while `trigger` is a debounce and hold.

docs/interface/dashboards.md

@@ -92,6 +92,15 @@ it, so swapping the store is a change to one flow and nothing else. The answer
 also states what it was computed for, so an answer to a different question is
 ignored rather than two charts overwriting each other's picture.
 
+!!! note "Drop the bucket that is still filling"
+
+    The request carries a window and an interval, and the binning is the flow's
+    own work — so the newest bucket only ever holds the part of an interval
+    that has elapsed. Drawn, it reads as a fall that never happened. The
+    engine's own [Activity charts](index.md#activity) end on the last closed
+    bin for that reason; a flow answering a chart has to drop or hold back its
+    newest bucket the same way.
+
 ## Media tiles
 
 A media widget draws what its message points at: a picture, a clip with

docs/reference/node-types.md

@@ -126,7 +126,7 @@ thing configured elsewhere.
 
 ### Inject
 
-**`inject`** — emit a value on request, on a timer, or when the flow starts.
+**`inject`** — emit a value on request, on a schedule, or when the flow starts.
 
 | Setting | Default | Notes |
 |---|---|---|
@@ -137,8 +137,9 @@ thing configured elsewhere.
 | `at_start` | `false` | emit once when the flow starts |
 | `start_delay` | `1.0` | how long to wait before that first emission |
 
-The most-placed trigger in a real installation — mostly as a button someone
+The scheduler: a `cron` expression here is what makes a flow run by the clock.
-presses.
+It is also the most-placed node in a real installation — mostly as a button
+someone presses.
 
 ### Delay & schedule
 
@@ -169,7 +170,9 @@ needs a busy cascade slot waits for one.
 
 ### Trigger
 
-**`trigger`** — send one value now and another once things go quiet.
+**`trigger`** — send one value now and another once things go quiet. Despite
+the name, a debounce and hold rather than a scheduler: everything it sends
+starts from a value arriving. For a cron tick, see [`inject`](#inject).
 
 | Setting | Default | Notes |
 |---|---|---|