add CID-derived cap-ref fallback for missing/invalid refs
New shared module src/lib/cap-ref.js provides hashTo3Words (SHA-256 →\n3 BIP39 words) and resolveRef, which returns the record's ref when\nvalid or a deterministic fallback derived from its CID.\n\n- skim, vet, firehose: use resolveRef so every cap displays a ref\n- ship: import shared REF_PATTERN instead of inlining\n- Add @scure/bip39 dependency for the English wordlist