e1608: a configurable generator update rate, and the achieved rate in the Analog out panel

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/claude/probe-readings.md

@@ -1838,7 +1838,7 @@ kind, so a run without it never shows that kind. The `form` line appears once pe
 - `kinds=udps,e1608,flatudp,probe`: a missing kind means `register_builtin_sources()` was not called before `parse_args()`,
   or the env var gate is wrong.
 - `round_trip=0`: a form's `write` and `read` disagree about a key -- a renamed `SourceConfig` key, or an
-  absent key that was not defaulted. `valid=0` is a default configuration the form refuses. The e1608 form's sample sets address, port, scan_rate, mode, ai1, trigger, dir1 and plot0; a mismatch names one of those. The flatudp sample sets port, bind, multicast, iface, rate, endian and signals.
+  absent key that was not defaulted. `valid=0` is a default configuration the form refuses. The e1608 form's sample sets address, port, scan_rate, mode, ai1, trigger, dir1, plot0 and gen_rate; a mismatch names one of those. The flatudp sample sets port, bind, multicast, iface, rate, endian and signals.
 - `panel disconnected: sensitive=0 present=1`: **disable, don't hide.** `present=0` is a panel that was hidden
   or never added; `sensitive=1` is a panel that stays live with no source behind it.
 - `panel connected: sensitive=1`: anything else means `apply_source_panels` acted on the wrong widget (it must
@@ -1865,6 +1865,8 @@ The UDPS run has no `source-` page in `side_stack`, because the UDPS kind has no
 [e1608] scan socket closed by the board
 [e1608] reconnect: connects=2 connected=1 ok=1
 [e1608] resumed: frames_before=612 frames_after=662 ok=1
+[e1608] generator: requested=100.0 achieved=99.7 panel='100 Hz (requested 100 Hz)' ok=1
+[e1608] generator stopped: achieved=0.0 panel='off (requested 100 Hz)' ok=1
 [e1608] scan: found=1 ip=172.21.121.113 mac=00:80:2f:00:16:08 status='1 board found' fill_addr=1 fill_mac=1 rescan_replaced=1 ok=1
 ```
 
@@ -1901,6 +1903,17 @@ the one `[e1608] handshake with ...: Connection refused` line, `stream: ... sign
   drop (neither the scan read nor the status check raised it), `resumed: ok=0` is a reconnect that did not restart
   the scan (it also reads 0 when `connects` is still 1, since a frame count that grows on a link that never dropped
   proves nothing).
+- `generator: requested=100.0 achieved=99.7 ... ok=1`, `generator stopped: ... ok=1`
+  (`UDPSCOPE_PROBE_E1608_GEN=1500`, a run of its own with `gen_rate=100`): `requested` is `gen_rate`, `achieved`
+  the source's own measurement (generator ticks that wrote, per second of wall time, over a window of about 1 s),
+  `panel` the subtitle of the Analog out panel's "Update rate" row. `ok` needs `achieved` within 70% to 110% of
+  `requested` **and** the panel to quote the requested rate; the mock answers at once, so it reads within a
+  percent of `requested`. Far below is a `run_timers()` that re-arms with a constant (the 20 ms the setting
+  replaced reads 50) or a tick that runs late; `panel='off'` while `achieved` is non-zero is a panel that
+  did not refresh (it ticks only while its page is on screen) or one that reads the wrong readout. This line says
+  nothing about a real board, whose DAC writes are slower; there the same row is the measurement. The stopped
+  line must read `achieved=0.0` and a panel that starts with `off`; a non-zero value is a rate that
+  `update_gen_flags()` did not reset when the last generator stopped.
 - `scan: found=1 ... ok=1`: the form's **Scan network** row against the mock. `found` is the result rows after
   the first scan; `0` with the second line `did not answer` is an environment with no up, non-loopback
   broadcast interface that reaches the mock (or a refused broadcast), **not a pass**. `ip` is the listed address