v0.7.0: Select dropdown with fuzzy filter

Select widget: list of options with keyboard navigation (up/down/enter/esc,
ctrl+n/p), case-insensitive substring filter with character-set Jaccard
fuzzy fallback, category headers, viewport culling, on-select callback.

Fixed from subagent review:
- Category filter return-from bug: categories kept in filtered set
- Dead trigram code removed (string-trigrams, trigram-score)
- Exports cleaned up (removed unused trigram exports)
- Character-set Jaccard replaces trigrams (better for short strings)

25 select tests, 100% GREEN.
196 total (27 backend + 58 box + 60 input + 26 scrollbox/tabbar + 25 select)

src/components/select-package.lisp

@@ -0,0 +1,13 @@
+(defpackage :cl-tui.select
+  (:use :cl :cl-tui.backend :cl-tui.box :cl-tui.layout :cl-tui.input)
+  (:export
+   #:select #:make-select
+   #:select-options #:select-filter
+   #:select-selected-index #:select-on-select
+   #:select-layout-node
+   #:select-filtered-options
+   #:select-next #:select-prev
+   #:select-visible-options
+   #:select-handle-key
+   #:render
+   #:fuzzy-match-p))