Say it in icons, and put the whole backend behind four tabs

Six things Bryan asked for, which turned out to be one change: the app had
no icon set, so every one of them was blocked on having somewhere for icons
to come from.

That somewhere is dev-updater's arrangement, ported: a Nerd Fonts subset
committed as an asset, drawn as text. `Gear.kt`'s hand-drawn canvas gear
argued against icon fonts because a system font may not have the glyph and
whoever gets the empty box is never the person who wrote it. The objection
is right about *relying* on a system font and the answer is to ship the
glyph, so the file is gone and its reasoning is restated in `NerdIcons.kt`
rather than deleted -- otherwise the next reader re-derives it. `md-cog` and
`md-refresh` are dev-updater's own codepoints, because a cog means the same
thing in both apps.

The root screen's four words under the title are now four tabs, and the two
that act on the whole screen -- settings and refresh -- moved up onto the
title row as glyphs. That row's old comment recorded that a fifth word would
have had nowhere to go; tabs also say something the words did not, which is
that sessions, import, models and setups are four views of one backend
rather than four errands. Refresh feeds whichever tab is showing. Import,
models and setups lose their headings and their Back buttons, since the tab
row is now both.

Usage is a dialog. It is checked *against* what you were reading -- "can I
start this" is asked with the transcript still on screen -- and it had no
navigation of its own, so the only thing its Back could mean was "put this
away". The button that opens it is a chart glyph coloured by the worst of
the machine's windows, so the row says whether the limits are worth opening
before anybody opens them.

One `quotaColor` now colours every bar that measures a quota: blue, yellow
at 75%, red at 95%. The session bar escalates where it used to sit blue at
every level, and the dialog's thresholds moved out of it. A download keeps
plain blue at every value -- it has no limit to approach, and colouring it
like one would say the opposite of what is happening. States that are not
measurements take the ordinary control colour, since blue is the low end of
this scale and would read as "checked, and fine" about a machine nobody
could reach.

Send and stop are the filled paper plane and the filled square. Send keeps
the word "Queue" while a turn is in flight, because that is what pressing it
then does, and an icon that does two things while looking identical would
promise something immediate and do something that waits.

Looked at on the emulator: all six glyphs render, the tabs and the system
back gesture between them, the dialog over a live session, and the bar
bands at 82% and 97% forced through a scratch build, since this account is
at 72/31/5 and would only ever have shown blue.

app/androidApp/src/main/kotlin/com/example/aiapp/Theme.kt

@@ -130,16 +130,43 @@ val warningColor: Color
     @Composable get() = Mocha.Yellow
 
 /**
- * How much of a quota window is gone, on the bar under a session's header.
+ * The fill of a progress bar that is only reporting how far along something is.
  *
- * Blue because that bar reports a quantity rather than a verdict: it sits on a screen the reader
- * opened to do something else, and the scheme's primary made it the loudest thing there. The usage
- * screen is where the same number turns [warningColor] and then [overLimitColor] -- somebody
- * looking at that screen came to be told where the limits are.
+ * Blue because a bar like this reports a quantity rather than a verdict, and the scheme's primary
+ * made it the loudest thing on a screen the reader opened to do something else. A download, or a
+ * compaction, has no limit to be near: it finishes. Only a bar measuring a *quota* escalates, and
+ * that one is [quotaColor].
  */
-val usageColor: Color
+val progressColor: Color
     @Composable get() = Mocha.Blue
 
+/**
+ * The fill of a bar measuring how much of a quota is gone: blue, then yellow, then red.
+ *
+ * One function rather than the same `when` written beside each bar, because the whole point of
+ * colouring by consequence is that the reader learns the step once -- two bars showing the same 80%
+ * in different colours teaches nothing except that the colour cannot be trusted. It reads as a
+ * difference in degree, which is all colour can carry: the states that differ in *kind* from this
+ * -- a window nobody could read, a machine that meters nothing -- are said in words elsewhere,
+ * because a reader has no way to tell those from an ordinary low number by colour alone.
+ *
+ * [percent] is the API's own 0-100 rather than a fraction, so callers pass what the server sent
+ * without each converting it first and one of them getting it wrong by a factor of a hundred.
+ */
+@Composable
+fun quotaColor(percent: Double): Color =
+    when {
+        percent >= OVER_LIMIT_PERCENT -> overLimitColor
+        percent >= WARNING_PERCENT -> warningColor
+        else -> progressColor
+    }
+
+/** Close enough to the limit to be worth seeing before starting something big. */
+private const val WARNING_PERCENT = 75.0
+
+/** Close enough that the next turn may be the one that is refused. */
+private const val OVER_LIMIT_PERCENT = 95.0
+
 /**
  * Code: a fenced block, an inline span, a tool's input.
  *