fix(sessions): hide misleading "0 files" in session list (#75)

session.summary is always a truthy object with files defaulting to 0
until the server populates real counts, so the session list always
rendered "· 0 files" regardless of actual changes. SessionInfo.tsx
already guards on `summary.files > 0`; apply the same guard in the
session list so it no longer shows a count that is never accurate.

Note: this does not make the count itself accurate — session.summary
is populated server-side and the opencode server currently never
updates it after a session runs. Showing correct counts needs either
a server-side fix or client-side aggregation from session message
parts; this PR only removes the always-wrong "0 files" text.

Partially addresses #55

Co-authored-by: engineer <engineer@macbookpro.lan>

app/(tabs)/index.tsx

@@ -78,7 +78,10 @@ function SessionItem({
         <View style={styles.sessionMetaRow}>
           <Text style={[styles.sessionMeta, isDark && styles.metaDark]}>
             {formatTime(session.time.updated)}
-            {session.summary && ` · ${session.summary.files} files`}
+            {/* summary is always present but files defaults to 0 until the
+                server populates it — only show the count when it's meaningful,
+                matching the SessionInfo panel's `summary.files > 0` guard (#55) */}
+            {session.summary && session.summary.files > 0 && ` · ${session.summary.files} files`}
           </Text>
           {shortDir && (
             <View style={styles.sessionDirBadge}>