Degauss 0.3.0

Five features, a new home for the install, and a round of fixes. Every
issue in the tracker at the time of this release is closed by it.

Upgrading

Nothing to do, whichever version you come from. Degauss now lives in
Scripts/.config/degauss, where the rest of the ecosystem keeps such
folders, and on the first start after updating, degauss.sh says
Migrating Degauss data... on the console, moves everything over, and
removes the old folder. Your settings, resume state and index carry
over; a degauss.toml, systems.toml or logo you edited stays the
active copy; anything else you kept in the folder follows the move
untouched. If an install ever looks wrong, the binary
can now look itself over:

/media/fat/Scripts/.config/degauss/degauss --check-install

New

• Themes. A Theme row in Options switches named palettes, each one a
  small .toml file in themes/ beside degauss.toml. Three ship as
  starting points: Amber, Mono, and Blue-Orange. A theme names any
  subset of the colour roles, bare or under a [colors] header, so the
  block from degauss.toml pastes in unchanged; an extra logo key
  paints the wordmark as a flat silhouette. Switching repaints
  everything live, covers included. (#3)
• Left and right are yours. A new Options row decides what the two
  best-placed buttons do while browsing: Scroll speed change (the
  default, as before), Letter, Page, or Direction. Letter and Page
  repeat while held at the same cadence as a held up or down; Direction
  frees up and down to move whole rows in Tiled. (#4)
• Come back to where you were. Every folder remembers the row it was
  left on, by the game itself rather than its position, so a folder
  whose contents changed still comes back to the same game. The groups
  remember too: Console left on one system comes back to it even after
  a walk through Computer. Favouriting or hiding a game deep in a long
  list no longer snaps the cursor away, including when the hidden game
  was the one under the cursor. (#6)
• Rebuild one system. The contextual menu gains Rebuild this
  system list:
  it reads the system on screen again in seconds and leaves the other
  hundred alone. Adding games to one system no longer costs a
  whole-card read. (#7)
• Games on external storage. USB sticks, the network share and the
  CIFS mount are searched without any setup, in the order MiSTer's own
  loader uses: /media/usb0..5/games, /media/network/games,
  /media/fat/cifs/games, then the card. For each system folder the
  first place that has it wins, exactly as the stock menu would load
  it. Storage is found at startup or on the next Rebuild all system
  lists.
• Two more typefaces. Smooth 2 (Roboto Condensed Bold) and Pixel 2
  (Tamzen Bold): bolder without being wider, for screens where the
  originals run thin.

Fixed

• A favourite is saved under the name on screen, not the filename, so
  Blazing Star no longer becomes Blazing Star (blazstar) on the
  shelf. (#9)
• A new favourite appears under Favourites immediately, without a full
  rebuild. (#8)
• Declining to launch, or a launch refusal, no longer leaves Degauss
  stuck behind its own message: any button dismisses a message, and the
  overlay says so. (#5)
• Inside Favourites, the contextual menu now knows where it is: every
  row there carries its heart, the menu offers Remove from favourites,
  and choosing it removes the favourite under the cursor. (#14)

Changed

• The Options screen is one grouped list: moving through lists,
  looks, ordering, what is shown, the physical screen, the machine-wide
  acts, and a Developer door holding just the diagnostics. Screensaver
  and the screen-geometry settings sit on the main screen now, and the
  names say what they govern: Left and right behaviour, Folders before
  games, Random game behaviour, Show Other folder, Show Utility folder,
  Show systems with no games.
• Fresh installs start at 3x scroll with artwork loading up to
  6x; saved settings win over both, as always.
• The full rebuild is called what it is: Rebuild all system lists
  in Options, with the progress overlay saying Indexing all systems;
  the one-system rebuild reports Indexing list.
• PgUp and PgDn page on every screen, not only the games list.
• A left_right value nothing answers to is refused when the config is
  read, like a bad colour, instead of silently meaning the default.

Under the hood

The migration is rehearsed in CI against nine upgrade shapes, and the
exact configs both old releases shipped are parsed by the test suite
forever, so a config key can never be renamed or removed out from under
a migrated card. The Downloader database moves to the new paths with
this release; Downloader installs clean up their old files on the next
run by themselves.