Give Activity a genuine ninth colour: --tt-orange

Requested directly: "can we make activity orange". The locked eight
palette had already run out at six legible text colours (Watch's blue
was the last one, and it's already a contrast exception); a dithered
swatch alone read as unfinished, and dithering the word itself
rendered as illegible static — tried and reverted this session.

--tt-orange (#ff8000) is defined in base.css right after the locked
eight, clearly marked as a deliberate, acknowledged one-off exception
to "eight colours, no ninth" rather than a secretly-smuggled-in tint.
Same flat text+swatch treatment as every other fastext key. Updated
CLAUDE.md's discipline 1 and DESIGN.md's Locked Eight Rule to name the
exception explicitly, so it reads as a documented decision next time
someone audits the palette, not a bug.

CLAUDE.md

@@ -66,7 +66,12 @@ the user's Unraid home server. Server-side project directory is still named
   than a variation:
   1. **No in-between tone.** There are eight colours (the teletext
      primaries). A mid-grey is an ordered dither of two of them, never a
-     ninth colour.
+     ninth colour — except `--tt-orange`, the one deliberate, acknowledged
+     break in `base.css`, added when the fastext nav ran out of legible
+     colours for its eighth destination (Activity) and dithering the
+     word itself proved illegible. Treat a *second* ninth colour showing
+     up as the regression this discipline warns about; this one is a
+     one-time, explained exception, not a precedent.
   2. **No enclosure.** Nothing is surrounded by a border or a box. There is
      zero `border-radius` in the codebase. Grouping is a coloured field row
      (`.tt-field`), indentation, and weight. This is the single thing the
@@ -106,23 +111,27 @@ the user's Unraid home server. Server-side project directory is still named
     other nav, so it needs no scroll to reach. The index overrides it
     with `HOME_FASTEXT`, the original four-entry row, as its own closing
     line, since its body already lists every destination once. Every
-    destination gets its own distinct mark. Six get a flat colour, text
-    and swatch both: Index/Library/Discover/System keep their `r`/`g`/
-    `y`/`c` shortcut; Requests gets magenta/`--pending` with no
-    shortcut (a deliberate fit — Requests already is "waiting on a
-    human" everywhere else magenta appears); Watch gets blue (`.k-blue`)
-    with no shortcut. Blue is a known exception to the app's own 4.5:1
+    destination gets its own distinct flat colour, text and swatch
+    both: Index/Library/Discover/System keep their `r`/`g`/`y`/`c`
+    shortcut; Requests gets magenta/`--pending` with no shortcut (a
+    deliberate fit — Requests already is "waiting on a human"
+    everywhere else magenta appears); Watch gets blue (`.k-blue`) with
+    no shortcut. Blue is a known exception to the app's own 4.5:1
     text-contrast bar (it clears ~2.4:1 on black) — kept anyway, at the
     visitor's request, over the alternative of a swatch-only accent
-    that read as unfinished next to six fully-coloured neighbours.
-    Activity gets an ordered-dither swatch (`.k-dither`, same mechanism
-    as `--dither-mid`) instead of a flat colour — the one other legal
-    way to get a distinct mark without a ninth hue. Settings alone
-    keeps plain ink with no swatch treatment — deliberately, as the one
-    page with no live status of its own. Whichever entry matches the
-    current page renders as a `.fastext-here` span instead of a link —
-    a page linking to itself did nothing, so it isn't offered as a
-    click.
+    that read as unfinished next to its fully-coloured neighbours.
+    Activity gets `--tt-orange` (`.k-orange`) — a genuine ninth colour,
+    the one destination that breaks "eight colours, no ninth"
+    outright, defined and explained in `base.css` right after the
+    locked eight. It's there because the palette ran out at six
+    (dithering a swatch alone read as unfinished, and dithering the
+    word itself renders illegible) and the visitor wanted every
+    destination to look different, not merely as different as eight
+    colours allow. Settings alone keeps plain ink — deliberately, as
+    the one page with no live status of its own. Whichever entry
+    matches the current page renders as a `.fastext-here` span instead
+    of a link — a page linking to itself did nothing, so it isn't
+    offered as a click.
   - **Nothing is clipped, hidden, or sticky.** All seven page numbers and
     every fastext entry stay visible at every width, reflowing to another
     row rather than scrolling, truncating, or folding into a menu. No