file manager: tree height fits the free viewport space (sw otaman-v175)

The tree box was capped at a fixed 65vh, which ignored the chrome above it
(header, tabs, status, sub-tabs, sort/probe row), so the page itself grew a
scrollbar once the tree hit its cap. pysimFsFitTree() now caps it to
innerHeight - top - 12px at runtime (the inline 65vh stays as the no-JS
fallback), re-run on resize, on render, on sub-tab/tab entry and when the
probe status line appears.

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'otaman-v174';
+const CACHE = 'otaman-v175';
 const URLS = [
   'index.html',
   'help.html',