hermes brand kit: inner V-fold now reads on every surface

Before: the on-sky lockup had a dark mark with dark cutouts — the fold
V-shape disappeared because the cutouts matched the mark colour instead
of the sky backdrop. Same on cream.

Now three per-surface mark variants, cutouts coloured to match the
expected background so it shows through:
  mark.svg          sky body  + navy cutouts   → dark panel
  mark-on-sky.svg   navy body + sky cutouts    → sky-blue surface
  mark-on-light.svg navy body + cream cutouts  → light surface

Logo lockups rebuilt the same way: logo-horizontal-on-sky.svg uses the
dark+sky mark variant, logo-horizontal-light.svg uses the dark+cream
mark variant, same for stacked.

Branding page's on-sky / on-light preview cells repointed at the new
variants. addon.json bumped to 0.2.6 (same mark, re-emitted from
pipeline for byte parity with the sites).

hermes/branding/index.html

@@ -99,8 +99,8 @@
     <div class="cell"><img src="../favicon.svg" alt="" width="32" height="32"><small>32 px</small></div>
     <div class="cell"><img src="../favicon.svg" alt="" width="64" height="64"><small>64 px</small></div>
     <div class="cell"><img src="../favicon.svg" alt="" width="96" height="96"><small>96 px (panel)</small></div>
-    <div class="cell cell-sky"><img src="../favicon.svg" alt="" width="64" height="64"><small>on sky</small></div>
-    <div class="cell cell-light"><img src="../favicon.svg" alt="" width="64" height="64"><small>on light</small></div>
+    <div class="cell cell-sky"><img src="mark-on-sky.svg" alt="" width="64" height="64"><small>on sky</small></div>
+    <div class="cell cell-light"><img src="mark-on-light.svg" alt="" width="64" height="64"><small>on light</small></div>
   </div>
 
   <div class="dl-row">