fix(web): stop presenting an unscored case as a failed analysis, and four smaller things

From clicking through the redesigned UI:

- scoring a case without a model registry painted a red failure across a case that had in
  fact analysed fine. It is now a quiet note saying the model term contributes 0, because
  scoring is an optional fourth of the rank, not the analysis.
- the MLflow default moves to port 5001. On macOS, AirPlay Receiver owns 5000, which is why
  the registry answered "403" rather than refusing the connection; docker-compose publishes
  5001 to match.
- a funnel step that kept nothing drew a visible bar. Zero now draws zero.
- "1 candidates".
- the funnel's fixed grid columns forced a horizontal scrollbar on the report.

The report also lists the top undecided candidates now: the first thing anyone opens has no
decisions in it, and "Shortlisted (0)" alone said nothing about what the tool found.

Tests: api 77, web 32; ruff, mypy, svelte-check clean.

web/src/routes/cases/[id]/+page.svelte

@@ -3,6 +3,7 @@
   import { api, type Candidate, type CandidatePage, type Case, type Job, type VariantDetail } from '$lib/api';
   import { poll } from '$lib/poll';
   import { formatElapsed, latestStep } from '$lib/progress';
+  import { plural } from '$lib/candidates';
   import CandidateRow from '$lib/components/CandidateRow.svelte';
   import Funnel from '$lib/components/Funnel.svelte';
   import VariantPanel from '$lib/components/VariantPanel.svelte';
@@ -22,6 +23,7 @@
   let busy = $state(false);
   let scoring = $state(false);
   let error = $state<string | null>(null);
+  let scoreNote = $state<string | null>(null);
   let now = $state(Date.now());
   let stopPolling: (() => void) | null = null;
 
@@ -82,8 +84,10 @@
     scoring = true;
     try {
       await api.score(data.caseId);
+      scoreNote = null;
     } catch (e) {
-      error = `Scoring failed: ${(e as Error).message}`;
+      // Scoring is optional: without a model the rank simply loses one of its four terms.
+      scoreNote = (e as Error).message;
     } finally {
       scoring = false;
     }
@@ -138,6 +142,9 @@
 </div>
 
 {#if error}<p role="alert">{error}</p>{/if}
+{#if scoreNote}
+  <p class="note">Variants are unscored, so the model term contributes 0 to every rank. {scoreNote}</p>
+{/if}
 
 {#if running}
   <p class="progress" aria-live="polite">
@@ -177,7 +184,7 @@
 
   <div class="triage">
     <div class="candidates">
-      <p class="muted">{page.total} candidates ranked by phenotype fit, rarity, consequence and model score</p>
+      <p class="muted">{plural(page.total, 'candidate')} ranked by phenotype fit, rarity, consequence and model score</p>
       {#each page.items as candidate, i (candidate.variant.id)}
         <CandidateRow
           {candidate}

web/src/routes/cases/[id]/report/+page.svelte

@@ -57,6 +57,16 @@
       <p class="muted">Nothing shortlisted yet.</p>
     {/each}
 
+    {#if report.top.length}
+      <h2>Top candidates, not yet decided ({report.top.length})</h2>
+      {#each report.top as item (item.variant.id)}
+        <div class="reportitem">
+          <h3>{item.variant.gene ?? 'intergenic'} <span class="coord">{item.variant.chrom}:{item.variant.pos} {item.variant.ref}&gt;{item.variant.alt}</span></h3>
+          <Chips chips={evidenceChips(item, termCount)} />
+        </div>
+      {/each}
+    {/if}
+
     {#if report.dismissed.length}
       <h2>Dismissed ({report.dismissed.length})</h2>
       <ul class="dismissed">