feat(ext/setup): zxcvbn strength meter + score>=3 gate (audit H3)

Replaces the ad-hoc char-class passphraseStrength() with a 5-segment
bar backed by a SW round-trip to rate_passphrase (zxcvbn). Input
handler debounces 150ms so we don't hammer the worker per keystroke.

The create-vault button is disabled unless the last score is ≥ 3
(zxcvbn's "safely unguessable" threshold), and the handler re-rates
synchronously on click as defence-in-depth. Label flips between "Too
weak" (red) and "Strong enough" (green).

Also:
- rewrites the vault-creation path to use the typed-item unlock +
  manifest_encrypt APIs (derive_master_key/encrypt_manifest are gone);
  the new initial manifest is { schema_version: 2, items: {} }.
- wasm.d.ts is now a pure `declare module 'relicario-wasm'` block;
  tsconfig's stale `paths` alias is removed.
- @ts-nocheck removed from setup.ts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

extension/setup.html

@@ -49,23 +49,38 @@
     }
 
     .strength-bar {
+      display: flex;
+      gap: 3px;
+      margin-top: 6px;
+    }
+
+    .strength-bar .seg {
+      flex: 1;
       height: 4px;
       background: #21262d;
       border-radius: 2px;
-      margin-top: 6px;
-      overflow: hidden;
+      transition: background 0.2s;
     }
 
-    .strength-bar-fill {
-      height: 100%;
-      border-radius: 2px;
-      transition: width 0.2s, background 0.2s;
-    }
+    /* zxcvbn score-driven colors. Higher-scored bars light up earlier bars too. */
+    .strength-bar.s0 .seg.i0 { background: #f85149; }
+    .strength-bar.s1 .seg.i0,
+    .strength-bar.s1 .seg.i1 { background: #db6d28; }
+    .strength-bar.s2 .seg.i0,
+    .strength-bar.s2 .seg.i1,
+    .strength-bar.s2 .seg.i2 { background: #d29922; }
+    .strength-bar.s3 .seg.i0,
+    .strength-bar.s3 .seg.i1,
+    .strength-bar.s3 .seg.i2,
+    .strength-bar.s3 .seg.i3 { background: #3fb950; }
+    .strength-bar.s4 .seg { background: #3fb950; }
 
-    .strength-bar-fill.weak { background: #f85149; width: 25%; }
-    .strength-bar-fill.fair { background: #d29922; width: 50%; }
-    .strength-bar-fill.good { background: #3fb950; width: 75%; }
-    .strength-bar-fill.strong { background: #58a6ff; width: 100%; }
+    .strength-label {
+      font-size: 11px;
+      margin-top: 3px;
+    }
+    .strength-label.weak   { color: #f85149; }
+    .strength-label.strong { color: #3fb950; }
 
     .success-box {
       background: #0d1b0e;