improved timing acq

CLAUDE.md

@@ -229,6 +229,14 @@ Two lines of the self-check output are assertions in disguise:
   first run's values, and the signals it names must come back *acquired* (a `row 0 slot 0
   -> channel ... samples=N` line). Delete the file before a run whose layout you did not
   mean to inherit (`127.0.0.1_9540.toml` and friends accumulate otherwise).
+- **The export's `time`/`stream_time` columns must be strictly increasing and evenly
+  spaced.** Check the written file, not just the probe: `np.diff(t)` with no `<= 0` and
+  `rows / (t[-1] - t[0])` equal to the stored rate (the `ch` line's figure). Duplicate or
+  backwards stamps mean the recorded timeline holds two clocks or a collapsed cadence —
+  the two ways this has broken: a per-frame choice of time source (now sticky, see the
+  README) and a per-sample step derived from the client's `lost` counter (now the
+  stream's measured arrival cadence). A `rows=` count far below the span times the rate
+  is the other signature, that of a table cut from the LOD pyramid.
 - `badge frames: lit=L dim=D idle=I` — the activity badge's phase per frame. Over a run
   that acquired anything **both `lit` and `dim` must be non-zero**: that is what "it
   blinks" means, and a badge stuck lit is indistinguishable from a working one in a