feat(frontend): unlocks/inventory UI, sigil designer, listening-tool EVP threshold

Workstream F of the character-depth/ghost-log spec.

- InventoryPanel.tsx: essence balance, owned unlocks/items (terminal
  listing + Codex-style rarity-glow borders on items), and a buy flow
  for a small fixed unlock catalog (currently just "listening_tool",
  the only key the contract names) with afford/can't-afford button
  states. Prices are fetched from a best-guess /api/inventory/catalog
  endpoint and fall back to a flagged "(est.)" price sourced from the
  spec's own worked example when that endpoint isn't available yet —
  the contract doesn't define a price-list REST shape.

- SigilDesigner.tsx + lib/sigil.ts: constrained geometric builder —
  points snap to 24 fixed clock-face slots around a circle, capped at
  12 to match the backend's payload limit, connected in placement
  order. Five hand-drawn stroke-only rune glyphs (eye/crescent/key/
  spiral/thorn) overlay the center. Point-cap enforcement, rune
  selection and payload-shape building are pure functions in
  lib/sigil.ts, unit-tested directly. Saves via POST
  /api/inventory/sigils (path inferred; payload shape matches the
  contract exactly: {"points": [[x,y],...], "rune": str}). Art
  direction: the builder itself reads like a plotting/debug tool
  (crosshair cursor, monospace coordinate HUD) while the rendered
  lines + rune glow violet, consistent with GhostGlyph's conventions.

- lib/evp.ts: new evpThresholdDb(hasListeningTool) pure function and
  EvpListener.start() now accepts { hasListeningTool } to lower the
  EVP anomaly threshold (8dB -> 4dB) when the unlock is owned — wired
  from useAuth().user.unlocks in SeancePage's EvpPanel, a real
  gameplay effect on which faint signals register as anomalies.

- api.ts User type gains unlocks/essence per the contract's /auth/me
  extension; new InventoryPage.tsx mounts both components behind auth
  at /inventory, linked from the séance nav.

166/166 tests pass (137 pre-existing + 29 new), i18n coverage check
clean, tsc -b clean.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

frontend/src/pages/InventoryPage.css

@@ -0,0 +1,80 @@
+/* InventoryPage — thin shell around InventoryPanel + SigilDesigner,
+   matching CodexPage.css's page-chrome conventions. */
+
+.inventory-page {
+  min-height: 100vh;
+  width: 100%;
+  background:
+    radial-gradient(ellipse 80% 50% at 50% -10%, rgba(178, 107, 255, 0.08), transparent 70%),
+    var(--qm-bg);
+  color: var(--qm-text);
+  font-family: var(--qm-font-ui);
+  padding: 2rem clamp(1rem, 4vw, 3.5rem) 5rem;
+  box-sizing: border-box;
+  position: relative;
+}
+
+.inventory-overlay {
+  position: fixed;
+  inset: 0;
+  pointer-events: none;
+  z-index: 10;
+  background:
+    repeating-linear-gradient(
+      0deg,
+      rgba(255, 255, 255, 0.022) 0px,
+      rgba(255, 255, 255, 0.022) 1px,
+      transparent 1px,
+      transparent 3px
+    ),
+    radial-gradient(ellipse at center, transparent 55%, rgba(0, 0, 0, 0.6) 100%);
+}
+
+.inventory-loading {
+  min-height: 100vh;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  color: var(--qm-green);
+  font-family: var(--qm-font-ui);
+}
+
+.inventory-header {
+  text-align: center;
+  margin: 0 auto 2.2rem;
+  max-width: 760px;
+  position: relative;
+}
+
+.inventory-back {
+  color: var(--qm-dim);
+  text-decoration: none;
+  font-size: 0.8rem;
+  letter-spacing: 0.06em;
+}
+
+.inventory-back:hover {
+  color: var(--qm-green);
+}
+
+.inventory-title {
+  font-family: var(--qm-font-display);
+  font-size: clamp(1.8rem, 4vw, 2.6rem);
+  letter-spacing: 0.14em;
+  margin: 0.6rem 0 0.4rem;
+  color: #eef7f0;
+}
+
+.inventory-subtitle {
+  color: var(--qm-dim);
+  font-size: 0.9rem;
+  margin: 0;
+}
+
+.inventory-main {
+  max-width: 1100px;
+  margin: 0 auto;
+  display: flex;
+  flex-direction: column;
+  gap: 2.4rem;
+}

frontend/src/pages/InventoryPage.tsx

@@ -0,0 +1,47 @@
+// The Reliquary Shelf — the seeker's unlocks/items/essence and the sigil
+// designer, gated behind auth like SeancePage.
+
+import { Link, Navigate } from 'react-router-dom'
+import { useTranslation } from 'react-i18next'
+import { useAuth } from '../state/auth'
+import { InventoryPanel } from '../components/InventoryPanel'
+import { SigilDesigner } from '../components/SigilDesigner'
+import './InventoryPage.css'
+
+export function InventoryPage() {
+  const { user, checking } = useAuth()
+  const { t } = useTranslation()
+
+  if (checking) {
+    return (
+      <div className="inventory-loading" role="status">
+        {t('common.loading')}
+      </div>
+    )
+  }
+  if (!user) return <Navigate to="/enter" replace />
+
+  return (
+    <div className="inventory-page">
+      <div className="inventory-overlay" aria-hidden="true" />
+      <header className="inventory-header">
+        <Link to="/seance" className="inventory-back">
+          {t('inventory.back', { defaultValue: '← back to the séance' })}
+        </Link>
+        <h1 className="inventory-title">{t('inventory.pageTitle', { defaultValue: 'THE SHELF' })}</h1>
+        <p className="inventory-subtitle">
+          {t('inventory.pageSubtitle', {
+            defaultValue: 'what the veil has left you, and what it will still trade for',
+          })}
+        </p>
+      </header>
+
+      <main className="inventory-main">
+        <InventoryPanel unlocks={user.unlocks} essence={user.essence} />
+        <SigilDesigner />
+      </main>
+    </div>
+  )
+}
+
+export default InventoryPage

frontend/src/pages/SeancePage.tsx

@@ -254,6 +254,10 @@ function SeanceSession({ username }: { username: string }) {
             {t('nav.codex')}
           </Link>
 
+          <Link to="/inventory" className="seance-codex-link">
+            {t('nav.inventory', { defaultValue: 'inventory' })}
+          </Link>
+
           <span className="seance-user" title={username}>
             {username}
           </span>
@@ -464,7 +468,11 @@ function WirePanel() {
 
 function EvpPanel() {
   const { sendAnomaly } = useSeance()
+  const { user } = useAuth()
   const { t } = useTranslation()
+  // "listening_tool" unlock (GET /auth/me's `unlocks`) lowers the EVP
+  // detector's threshold so fainter deviations register — see lib/evp.ts.
+  const hasListeningTool = user?.unlocks?.includes('listening_tool') ?? false
   const [listening, setListening] = useState(false)
   const [pending, setPending] = useState(false)
   const [denied, setDenied] = useState(false)
@@ -526,7 +534,7 @@ function EvpPanel() {
             setBandDb(Number.isFinite(peak) ? peak : null)
           }
         },
-      })
+      }, { hasListeningTool })
       if (listenerRef.current === listener) setListening(true)
     } catch {
       if (listenerRef.current === listener) listenerRef.current = null