ui: flip tone relabel — "Pro" now maps to INTERMEDIATE, not NOVICE

Reverses the polarity of 71155a6 to match the actual semantics:

- "Novice" stays labelled "Novice" → glossary tooltips, plainer prose.
- "Intermediate" is relabelled "Pro" → terse, assumes fluency, no
  hand-holding. This is the mode an expert reader wants, so the "Pro"
  badge actually fits.

Backend tone values (NOVICE, INTERMEDIATE) are unchanged — no API,
prompt, or stored-preference impact. Only the display strings flip.

Also drops the .tone-toggle button min-width: 10em override added in
71155a6. With "Intermediate" gone from the visible label, the longest
remaining label is "Novice" (6 chars), which fits the shared 5.5em
just like the theme and language toggles.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/templates/settings.html

@@ -185,9 +185,9 @@
         <div class="settings-row__value">
           <div style="display:flex; gap:14px;">
             <label><input type="radio" name="digest-tone" value="NOVICE"
-              {% if (user.digest_tone or 'INTERMEDIATE') == 'NOVICE' %}checked{% endif %}> Pro</label>
+              {% if (user.digest_tone or 'INTERMEDIATE') == 'NOVICE' %}checked{% endif %}> Novice</label>
             <label><input type="radio" name="digest-tone" value="INTERMEDIATE"
-              {% if (user.digest_tone or 'INTERMEDIATE') == 'INTERMEDIATE' %}checked{% endif %}> Intermediate</label>
+              {% if (user.digest_tone or 'INTERMEDIATE') == 'INTERMEDIATE' %}checked{% endif %}> Pro</label>
           </div>
         </div>
       </div>