Browser \`structuredClone\` itself fails on Svelte 5 \$state Proxies
("Failed to execute 'structuredClone' on 'Window': [object Array]
could not be cloned") — it doesn't transparently unwrap the Proxy the
way I'd hoped. The structured-clone algorithm refuses any non-cloneable
host object, including Svelte's reactive wrappers.
JSON.parse(JSON.stringify(...)) traverses through the Proxy by reading
each property normally, producing a plain-data copy that Dexie can
serialise without complaint.
Mission payloads are pure JSON values (strings/numbers/arrays/objects)
so JSON-roundtrip is lossless. The new \`deepClone\` helper is local to
this file with a comment pointing at the structured-clone failure.
77/77 webapp tests still green.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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