badges: hide the Source badge when the source has no panel of its own

A Source pill that opens nothing (UDPS, Flat UDP, files) was noise. It is now shown only while the slide-over has a source page; the [badges] source line gains visible=.

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

docs/claude/probe-readings.md

@@ -2663,14 +2663,14 @@ signals list while the title and the badge marker still name `trigger`; `-1` whe
 ## `[sigbadges]`
 
 ```
-[sigbadges] enabled=4 badges=4 overflow=0 overflow_text=- plus_visible=1 dot_plotted=4 bar_h=36 bar_h_fixed=1 bar_min_w=251 opens=1 plus_opens=1
+[sigbadges] enabled=4 badges=4 overflow=0 overflow_text=- plus_visible=1 dot_plotted=4 bar_h=36 bar_h_fixed=1 bar_min_w=124 opens=1 plus_opens=1
 ```
 
 `UDPSCOPE_PROBE_SIGNAL_BADGES_MS` reads the signal badges. `badges` must equal `enabled` (the enabled, listed signals) while `enabled` is at most 6
 (`kMaxSignalBadges`); beyond that `badges=0 overflow=1 overflow_text=<N> signals plus_visible=0` (the "N signals" badge replaces the badges and the "+"). `dot_plotted` is the number of
 badges whose signal is on a plot (its dot is then the trace colour, not the unplotted grey). `bar_h` is the bar's allocated height and `bar_h_fixed=1` that neither it nor its natural
 height moved while one signal was switched off and on again (`rebuild_signal_panels()` each time), and that the badge count followed; `0` is a bar whose height depends on its content.
-`bar_min_w` is only a record: the scroller must keep it the same however many signals there are (it reads 251 with the UDPS mock's 4 and with the overflow forced on, and 244 against the E-1608 mock with one signal and with nine -- the overflow, `enabled=9 badges=0 overflow=1 overflow_text=9 signals plus_visible=0 bar_h=36 bar_h_fixed=1`; a value that grows with the signal count is a scroller that has stopped constraining the bar). `opens=1`: clicking the
+`bar_min_w` is only a record: the scroller must keep it the same however many signals there are (it reads 124 with the UDPS mock's 3 (the Source badge being hidden there) and with the overflow forced on, and 244 against the E-1608 mock with one signal and with nine -- the overflow, `enabled=9 badges=0 overflow=1 overflow_text=9 signals plus_visible=0 bar_h=36 bar_h_fixed=1`; a value that grows with the signal count is a scroller that has stopped constraining the bar). `opens=1`: clicking the
 first signal badge opens `signal:<name>` with the badge marked open and a second click closes it (`-1` when overflowed, there being no signal badges); `plus_opens=1` the same for the "+"
 (the overflow badge when overflowed) and the `signals` page.
 
@@ -2691,7 +2691,7 @@ gesture's threshold, the slide-over closing under it and the pointer-driven drop
 
 ```
 [badges] table_bad=0 trigger_state=off bar_h=36 bar_h_after=36 fixed=1 open_marked=1 page_open=1 closed_unmarked=1
-[badges] source name=UDPStreamer state=connected pages=0 switch_visible=0 can_target=0 second_page=- second_ok=-1 open_marked=-1 closed_unmarked=1 panel_min_w=0
+[badges] source name=UDPStreamer pages=0 visible=0 switch_visible=0 can_target=0 second_page=- second_ok=-1 open_marked=-1 closed_unmarked=1 panel_min_w=0
 ```
 
 `UDPSCOPE_PROBE_BADGES_MS` reads the badge bar under the plot. **Line 1** is the Trigger badge: `table_bad=0` (the rows of the 16-input
@@ -2700,12 +2700,13 @@ the same, and at least 36 px, before and after the `trigger` page was opened and
 moves), `open_marked=1` / `page_open=1` / `closed_unmarked=1` (the `udpscope-badge-open` class follows the slide-over's page, both ways; `0` on
 any is a badge that does not say its panel is open, or one that stays marked after it closed).
 
-**Line 2** is the Source badge, and every field has a value it must read:
+**Line 2** is the Source badge, which is **hidden when the source has no pages** (UDPS, Flat UDP, a file), and every field has a value it must read:
 
 - `name=` the source kind's name, as the badge shows it. The badge carries no link state (the status bar says it); there is no `state=` field.
 - `pages=` the number of slide-over pages the source kind contributes (`source-<id>`): `0` for UDPS, `2` for the E-1608 (`source-ao`, `source-dio`).
-  `can_target=0` with `pages=0` is the UDPS badge being a read-out rather than a button; `can_target=1` with `pages>0` is the button being live.
+  `can_target=0` with `pages=0` is the UDPS badge being untargetable, which goes with it being hidden; `can_target=1` with `pages>0` is the button being live.
   `can_target=1` with `pages=0` is a dead button that opens nothing.
+- `visible=` the badge being on screen: **`0` with `pages=0`** (hidden, by design: nothing to open), `1` with `pages>0`. `visible=1` with `pages=0` is a dead pill that was supposed to be hidden; `visible=0` with pages is a source panel nothing can open.
 - `switch_visible=` the segmented switch being on screen after the first source page was opened: `1` with two or more pages, `0` with one or none.
   A switch shown for a single page is a control that cannot change anything; hidden with two, the second panel is unreachable.
 - `second_page=` / `second_ok=` what `slideover_page()` read after the switch selected the second page, and whether it is that page. **`second_ok=1` with