v1.7.0

Interactive-viewer focus on top of 1.6.0. Major additions to the
ncurses TUI: mouse clicks, an in-place theme picker with XDG-spec
persistence, a vim-style : command line, and multi-file tabs.

Added

• TUI multi-file tabs — vv a.vcf b.bed c.parquet opens each
  file as a tab. Tab / Shift+Tab cycle. Each tab keeps its own
  scroll position, sort, filter, column-visibility set, search
  anchor, and chunk cache; switching back is instant. Status bar
  shows tab N/M: basename when more than one file is open.
  Non-interactive output modes (--tsv, --parquet, …) still
  process only the first positional — multi-file is TUI-only.
• TUI command line (: key) — vim/less-style typed-command
  prompt at the bottom of the screen. First verbs:
  • :<N> — jump to row N (matches the row-index column;
    out-of-range clamps to the last page). Closes the "scroll
    through millions of rows by hand" pain point.
  • :q / :quit — quit (vim muscle memory).
  • :theme NAME — text-driven theme switch (alt to the T
    overlay), with the same name set as --theme. Persisted to
    ~/.config/vv/config via the standard XDG path.
    Errors stay in the input bar so the line can be edited; Esc
    cancels. Extensible — future verbs (:reload, :w FILE, …)
    slot in without new key bindings.
• TUI theme picker (T key) — overlay listing every built-in
  theme; [*] marks the currently-active one, j/k move the
  cursor, Enter applies the choice. The new theme takes effect
  immediately (ncurses color pairs re-initialised in place) and
  the choice is persisted to ~/.config/vv/config
  ($XDG_CONFIG_HOME/vv/config if set) so future runs start with
  the same theme. Esc closes the overlay without changing.
• XDG-spec user config — vv now reads
  $XDG_CONFIG_HOME/vv/config (default ~/.config/vv/config)
  at startup. Format is plain INI-style key = value; lines
  starting with # are comments. Today only theme is read;
  the format is extensible — future preferences (default
  --threads, --decode-threads, etc.) slot in without breaking
  existing files. Writes are atomic (.tmp + rename) and preserve
  any comments / other keys in place. CLI flags always win over
  the config file.
• TUI mouse clicks — three additive bindings on top of the
  existing wheel-scroll: click a column header to sort by that
  column (toggle asc/desc on repeat; updates the active column
  for S / y); click a data row to scroll it to the top;
  double-click a data row to open the detail pane (same as
  Enter). Shift+drag continues to work as the universal escape
  hatch for native terminal text selection.