add Catppuccin Mocha theme (+ high-contrast sibling)

Ships catppuccin-mocha (faithful to the official Catppuccin Mocha
palette) and catppuccin-mocha-hc (high-contrast sibling per D-69 — the
faithful palette is never retuned to pass the gate). Both bundled and
gated: mocha clears baseline AA, mocha-hc clears the strict extended
set. Catppuccin MIT palette recorded in licenses.yaml.

Closes T-82 (Mocha + hc meets every acceptance bullet; faithful Latte
deferred — it can't clear baseline AA without retuning, a separate call).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,9 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Added
 
+- Catppuccin Mocha theme, plus a high-contrast `catppuccin-mocha-hc` sibling,
+  added to the bundled themes — switchable from the theme picker. Faithful to
+  the official palette (D-69). (T-82)
 - `clide ui open <reader> <id|path>` opens a doc in a GUI reader from the CLI —
   `tickets`/`decisions` by id, `markdown` by path — so an agent can surface what
   it's looking at on your screen. The drive-half complement to `clide status`. (T-231)