docs: source badge name only, no signals lock, the Add-a-signal page

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

README.md

@@ -104,7 +104,13 @@ src/ui_signal_page.cpp  the per-signal slide-over pages (`signal:<name>`)
 
 **The window.** The plot is the window. Under it sits a fixed-height **badge bar** (36 px). Its left
 part is the **signals**: one badge per *enabled* signal (a dot in the signal's colour, filled while the
-signal is plotted, and its name), then a `+` badge that opens the full signal list (`g` does the same).
+signal is plotted, and its name), then a `+` badge that opens the **Add a signal** page (`g` does the same). That page proposes only what can be
+*added*: the streamed signals that are not acquired and the math channels that are not computed, each row with
+the tick that acquires it (the row then leaves the page and the signal's badge appears), plus the `MATH`
+divider's `+` for a new math channel; when every signal is acquired a dim "every signal is acquired" line
+stands in for the list. While the bar has overflowed into the "N signals" badge the page lists the acquired
+signals too, since their rows are then the only way to each signal's page. There is no signal lock: a
+signal's page and the list always allow acquire, colour, calibration, the math editor and delete.
 A signal badge opens that signal's own page in the slide-over -- colour, calibration and the *Plot on N*
 buttons -- and is also the drag handle: drag it onto a plot to draw the signal there, or onto another
 badge to reorder them. Past **six** signal badges the bar shows a single **"N signals"** badge in their
@@ -112,7 +118,7 @@ place (it opens the list, and `+` is hidden): the E-1608's 8 analog inputs and c
 otherwise. The signal badges sit in a scroller, so the bar's minimum width, and with it the window's,
 never depends on how many signals there are. The badge order is kept **for the session only**; it is not
 written to the session file. The right-hand end carries two words-only badges: **Trigger** (`off`, `armed`, `capturing`, `triggered`
-or `disarmed`) and **Source** (the kind's name and `connected`/`disconnected`; a read-out, not a button,
+or `disarmed`) and **Source** (the kind's name only -- the link state is the status bar's; a read-out, not a button,
 for a source with no controls of its own, and for a file). A badge opens the **slide-over**: a 360 px
 panel laid over the plot's right edge, opaque, with its own title, a *Close* button and one scroller per
 page. The Trigger badge opens the trigger form; the Source badge opens the source kind's own panels
@@ -2937,11 +2943,10 @@ now — they are listed so they are not mistaken for anything else:
   tabs did not fit 320 px. It is **one dock** now, with no tab switcher: the cursors and the
   measurements in one scroller, shown from the start and insensitive until the stream has signals; `m`
   scrolls it to the cursors; the **signal list** is the `signals` slide-over page (`g`, or the `+` badge). The **trigger form** and a **source's own
-  controls** are pages of the slide-over, reached from the badge bar. Both panes also have a **locked** mode, which is what a returning user gets: the
-  trigger pane shows one line saying what it is set to, the signal list shows only the signals that are
-  on, and neither offers a control that changes the configuration -- each heading has an `[edit]` button
-  to switch to the full pane, and back. Dragging a signal's badge onto a plot still works while locked --
-  filling plots is not configuration. A signal's badge is dragged onto a plot, or onto another badge to
+  controls** are pages of the slide-over, reached from the badge bar. The trigger pane also has a **locked** mode, which is what a returning user gets: it
+  shows one line saying what it is set to and offers no control that changes the configuration -- its
+  heading has an `[edit]` button to switch to the full pane, and back. The signals have no lock: the
+  signals page only proposes what can be added, and the signal pages always allow editing. A signal's badge is dragged onto a plot, or onto another badge to
   reorder the badges (the order is kept for the session only); the slide-over closes for the length of the
   drag so there is something under the pointer to drop onto. A **first run** (no session file for that source) comes up
   unlocked, because configuring the host is what a first run is for. Each pane's heading also carries its **own switch**, the same control as the