Make username/password connect prompts hard to miss (issue #22)

The inline prompt bar previously had no explicit styling and rendered
in the same color as the rest of the tab; a tab showing the prompt in
the background had no indication anything needed attention. The bar
now uses a solid QPalette::Highlight fill with HighlightedText for the
label and a hand-drawn contrasting badge, and a background tab gets a
"(Needs input)" title suffix plus a distinct tab-bar color.

A first pass at the tab color (#6a1b9a) was reported unreadable in
dark mode; replaced with #ab47bc, tuned to match the visibility of the
existing connection-state colors.

Bump version to v2026.9.16.6.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/PROGRESS.md

@@ -209,6 +209,23 @@ Delivered:
   option, not the stale profile copy, is actually used) -- RDP has no
   equivalent fake-server test harness, so that side relies on mirroring
   the already-tested `m_activeOptions.password` pattern exactly
+- Issue #22: the inline username/password prompt bar used to just be a
+  plain `QWidget` with `setAutoFillBackground(true)` and no explicit
+  color, which meant it rendered in the same color as everything else
+  around it and was easy to miss -- especially on a tab that wasn't the
+  active one, where there was previously no indication anything needed
+  attention at all. Now uses a solid `QPalette::Highlight` fill with
+  `QPalette::HighlightedText` for the label (the OS theme's own
+  guaranteed-contrasting pair, so it stays correct under both light and
+  dark themes without a hardcoded color) plus a hand-drawn "?" badge
+  (not a themed `QStyle` icon, whose own colors are outside our control
+  and could land close in hue to the bar's background); a background
+  tab showing the prompt gets its title suffixed "(Needs input)" and its
+  tab-bar text colored distinctly from the four connection-state colors.
+  A first pass at the tab color (`#6a1b9a`) was reported unreadable in
+  dark mode -- its perceived luminance was well below the four existing
+  state colors -- and was replaced with `#ab47bc`, tuned to roughly
+  match their visibility
 - Robustness fix: an unrecognized `FramebufferUpdate` rectangle encoding
   used to abort the connection generically; `kAnnouncedEncodings` is now
   the single source of truth for what `SetEncodings` announces and what