feat(atlas): UX polish — legend + feedback-bus honesty + Plain declutter (#6, #8)

#6: always-visible legend keying the live-status colours (passed/running/failed),
the governance-gate colour, and the dashed feedback loop.
#8: the 08→TELOS loop is labelled "partly manual today" (honest, per PROJECT.md);
Plain view hides the jargon-dense substrate ribbon + technical footer, so a
non-technical viewer isn't shown koala/iguana/ns/assessor-loop proper nouns —
they remain in Technical view.

Frontend/CSS only; verified by screenshot. build/test/lint green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/web/static/cad-atlas.html

@@ -67,6 +67,15 @@
   .stagehead{min-height:64px}
   body.plain .stagehead{min-height:188px}
   .stage .node:first-of-type{margin-top:24px}
+  /* Plain view hides the jargon-dense infra ribbon + technical footer */
+  body.plain .substrate{display:none}
+  body.plain footer{display:none}
+  .legend{display:flex;gap:16px;flex-wrap:wrap;align-items:center;
+    padding:7px 22px;border-bottom:1px solid var(--line);background:var(--bg);font-size:11px;color:var(--dim)}
+  .legend .lbl{letter-spacing:1.5px;margin-right:2px}
+  .legend .lg{display:inline-flex;align-items:center;gap:6px}
+  .legend .lg i{width:11px;height:11px;border-radius:3px;display:inline-block;border:1px solid rgba(0,0,0,.35)}
+  .legend .dash{width:18px;border-top:2px dashed var(--violet);display:inline-block}
 
   .scroll{overflow-x:auto;padding:24px 22px 20px}
   .track{position:relative;display:flex;align-items:flex-start;min-width:max-content}
@@ -140,6 +149,14 @@
 
 <div class="substrate" id="substrate"><span class="lbl mono">SUBSTRATE</span></div>
 <div class="tl mono" id="timeline"></div>
+<div class="legend mono">
+  <span class="lbl">KEY</span>
+  <span class="lg"><i style="background:var(--green)"></i>passed / ready</span>
+  <span class="lg"><i style="background:var(--amber)"></i>running / waiting</span>
+  <span class="lg"><i style="background:var(--coral)"></i>failed / blocked</span>
+  <span class="lg"><i style="background:var(--gold)"></i>governance gate — must pass to advance</span>
+  <span class="lg"><span class="dash"></span> feedback loop · partly manual</span>
+</div>
 
 <div class="scroll">
   <div class="track" id="track">
@@ -246,7 +263,7 @@ function build(){
   const lastX=cs[cs.length-1], telosX=cs[1];
   loopPath.setAttribute('d',`M ${lastX} ${RAILY} L ${lastX} ${loopY} L ${telosX} ${loopY} L ${telosX} ${RAILY}`);
   loopLbl.setAttribute('x',(telosX+lastX)/2-90);loopLbl.setAttribute('y',loopY-8);
-  loopLbl.textContent=(STAGES[8]&&STAGES[8].trans_label?STAGES[8].trans_label+' · ':'')+'feedback bus';
+  loopLbl.textContent=(STAGES[8]&&STAGES[8].trans_label?STAGES[8].trans_label+' · ':'')+'feedback bus · partly manual today';
   // transition labels on the spine — the "what must be true to advance" story.
   // Always visible (default layer). Gate hops (04→05 human, 06→07 CI) in gold.
   const tg=document.getElementById('translabels'); tg.innerHTML='';