ui: a signal's page shows gain and offset as aligned rows with a pencil each, replacing Calibrate

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

docs/USER-GUIDE.md

@@ -66,8 +66,8 @@ the same signal twice, or onto another badge to reorder the badges. The colour i
 the same signal is the same colour wherever it appears.
 
 Clicking a signal's badge opens its own page: the colour, **Plot on** buttons for the rows, and
-**Calibrate** — gain and offset, applied at ingest, so the measurements and the export carry the same
-numbers the plot shows.
+**Gain** and **Offset**, shown as two aligned numbers with a pencil button each that edits that one value.
+They are applied at ingest, so the measurements and the export carry the same numbers the plot shows.
 
 ## 4. The window and navigation
 

docs/claude/invariants-math-channels.md

@@ -307,7 +307,7 @@ the assertion: `finite` must be about `M` minus the hole share, and `finite=0` b
   non-activatable -- a heading that highlighted under the pointer would read as a row you can plot --
   and it carries the `+` that creates a channel, appended even when there are none, because a `+` that
   waited for a channel to exist could never create the first one. A math row's menu is *Edit graph…*,
-  *Default colour*, *Delete*: no Information and no Calibrate, because calibration is applied at
+  *Default colour*, *Delete*: no Information and no Gain/Offset rows, because calibration is applied at
   ingest and a derived channel has no stream to describe, and no rename, because the node editor owns
   a channel's name and unit and a second place to change them would be a second answer to the same
   question. A row's tick is the channel's own switch and must reach `App::math` -- the copy the

docs/claude/probe-readings.md

@@ -1802,7 +1802,7 @@ direct manipulation, and `panes:` no longer carries a `signals=` field.)
 - **`body_visible=0`** is the settings being off screen, which is what makes the pane a couple of hundred
   pixels instead of 580 in `panels:`.
 - **The signals list has no lock.** It lists what can be *added* (see `signals panel:`), and the signal
-  pages always allow acquire, colour, calibrate, math edit and delete.
+  pages always allow acquire, colour, gain/offset, math edit and delete.
 
 ## `panel switches:` and the trigger panel's default sensitivity
 
@@ -2761,6 +2761,12 @@ the slide-over closed and the page was dropped by `signal_pages_sync()`. `pruned
 channel removed) and the slide-over was still on `trigger`, both by `slideover_page()` and by the stack's visible child; `0` is `signal_pages_sync()` parking the stack on the
 signals list while the title and the badge marker still name `trigger`; `-1` when there is no `trigger` page or no math channel could be added.
 
+A second line, `[signalpage] calibration identity=1/0 set=2.5/-1.25 pencils=2 pencil_edits_one=1`, reads the page's gain and offset rows
+(`udpscope-gain` / `udpscope-offset` labels, one string rule: `format_calibration()`, up to six decimals with trailing zeros dropped): `identity` is what an
+uncalibrated signal shows, `set` what the page shows after `set_calibration(2.5, -1.25)` and `signal_pages_sync()` (the Apply path), `pencils=2` the two edit
+buttons, and `pencil_edits_one=1` that the gain pencil opens a dialog titled "Gain" with exactly one spin button and that Apply changed the gain only
+(offset stayed -1.25) and refilled the label. `-1` is no pencil / no dialog; `0` is a dialog that edits both or a label that did not follow the model.
+
 ## `[sigbadges]`
 
 ```