CodeLookup: ICD-11 support (ingest WHO ICD-11 into the condition shard)

[horner]

Context

CodeLookup now has a coding-system mode (PR #333 branch codelookup-code-search):

• searchCodetypes prop — programmer fixes the system (e.g. ['ICD10'])
• codetypeOptions prop — user-facing segmented control (see the Conditions Only story: All | ICD-10 | SNOMED)
• Engine-side SearchOptions.codetypes filters both label and code-prefix matches

The filter is fully generic — ICD-11 mode is just codetypes: ['ICD11'] once the data exists. It doesn't yet: the source dataset (rxdb_utf8.MedicalCodify_search) has no ICD-11 rows (codetypes present: CVX, FDB, FDB MEDNAME, HCPCS, ICD10, ICD10PCS, ICD9, LabCorp Order, LOINC, LOINC Hierarchy, Measure, NDC, Quest Order, RxNORM, SNOMED US, ValueSet, VIS).

Task

Ingest the WHO ICD-11 MMS linearization into the codify pipeline so the condition shard carries ICD11 entries:

• Source: WHO ICD-11 release files or ICD-API (https://icd.who.int/icdapi) — codes + titles (+ index terms as aliases?); check license/attribution requirements
• Either add ICD-11 rows to MedicalCodify_search upstream, or add a supplemental input to packages/codify/scripts/build-index.mjs (external repo)
• Add ICD11 to the condition shard codetype list; rebuild .mcdx shards (git-lfs) — watch shard size / Cloudflare Pages 25 MiB cap
• Decide family grouping for ICD-11 codes in familyKey() (engine.ts) — current ICD-10 rule is letter+digit code-root; ICD-11 codes look like BD10, 8A61.0
• Check billableMask() (leaf-code rule) applicability to ICD-11 or scope it to ICD-10 only
• Add { label: 'ICD-11', codetypes: ['ICD11'] } to the Conditions Only story toggle
• Engine tests with ICD-11-shaped codes

Out of scope

ICD-10 ↔ ICD-11 crosswalk/mapping tables (separate ticket if needed).