feat(docs): in-place help pattern — explain a surface where it happens

New ChainInlineHelp (intro strip: what this is + what will happen, with
an optional 'Learn more' into the doc sheet) and ChainFieldHelp /
ChainFieldLabel (a '?' affordance per field). First applied to the
add-satellite dialog, which asked for a bare 'name' with no hint of
what a satellite is or does (usertest): it now leads with a plain
explanation + a federation 'Learn more', and the name field carries a
'?'. Both widgets are quiet by design.

Verified: field_help_test covers the widgets + that the dialog explains
itself; dialog_shots_test.dart (a reusable headed dialog-capture
harness) proved the layout in light + dark. Studio 0.76.0.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

CHANGELOG.md

@@ -6,6 +6,24 @@ lockstep.
 
 ## Unreleased
 
+### Added — explain it where it happens (0.76.0)
+
+- **In-place help pattern.** New `ChainInlineHelp` (a one-sentence
+  intro strip that says what a surface is and what will happen, with
+  an optional "Learn more" link into the doc sheet) and
+  `ChainFieldHelp` / `ChainFieldLabel` (a "?" affordance for a single
+  field). First applied to the add-satellite dialog, which used to
+  ask for a "name" with no hint of what a satellite even is
+  (usertest): it now leads with a plain explanation + a federation
+  "Learn more", and the name field carries a "?".
+- **Page help opens the RIGHT topic.** The Federation and Runs help
+  buttons silently fell back to the architecture doc — `federation`
+  and `runs` had markdown assets but no catalog entry, so
+  `showFaiDoc` resolved them to the first doc. Both are registered
+  now; a new `doc_help_wiring_test.dart` asserts every
+  `showFaiDoc('slug')` call has a registered entry AND both locale
+  assets, so a help button can never open the wrong topic again.
+
 ### Security (0.75.0)
 
 - **Sealed-area names are confidential by default.** The workspace