…in Jira Update

The Jira Update tool only accepted a single customFieldId + string
customFieldValue and wrote it raw, so it could not represent Jira's
option/user/cascading field shapes or set more than one custom field per
call.

- Add a `customFields` param: array of { fieldId, type, value } where type
  is text | number | select | multiselect | userpicker | multiuserpicker |
  cascading | raw. Serializes each into the Jira REST v3 fields shape.
- Add serializeJiraCustomField + buildJiraCustomFields helpers in
  tools/jira/utils.ts (mirrors toAdf; unit-tested directly).
- Merge legacy customFieldId/customFieldValue into the same pipeline as a
  raw passthrough; customFields wins on fieldId collision. Backward compatible.
- Custom fields are applied after simple fields under one PUT `fields` body,
  so simple + custom fields coexist. ADF description auto-wrap preserved.
- Extend jiraUpdateBodySchema contract and JiraUpdateParams; document the
  new shape in the tool param descriptions.
- Add route + utils unit tests asserting exact `fields` payloads.

…cading

Review round (Greptile P1 + Cursor):
- Contract: replace the permissive customFields `value: z.unknown()` with a
  discriminated union on `type`, so a shape/value mismatch (select as { label },
  userpicker as { email }, non-numeric number) is rejected at the boundary
  instead of serializing into a malformed value that would make Jira reject the
  whole combined update.
- Serializer: a cascading entry with no resolvable parent now returns undefined
  and is skipped, instead of emitting the literal "undefined" as the parent
  value. buildJiraCustomFields skips any entry whose serialization is undefined.
- Add tests for both plus boundary rejection of mismatched shapes.

Round 2 (Greptile + Cursor): cascading was validated more loosely than
select/userpicker — value accepted any record and child was z.unknown(), so an
unresolvable shape like { id: '10' } or an object-valued parent/child passed the
boundary and was then either silently dropped or serialized to '[object
Object]', rejecting the whole combined update. Constrain cascading parent/child
to scalars (matching the other option types); an arbitrary record now 400s at
the boundary. Adds a route test for the rejection.

… options

Round 3 (Greptile + Cursor) boundary hardening:
- cascading array values are capped at [parent, child] (.max(2)) so a 3+ element
  array is rejected instead of silently truncated by the serializer.
- text values must be strings; a bare number (common from LLM tool calls) is
  rejected rather than passed through to a string-typed Jira field.
- select/multiselect option values must be non-empty, so { value: '' } / { id: '' }
  / an empty array element can't serialize into an invalid Jira option.
Adds route tests for all three rejections.

…iases

Round 4 (Greptile): a cascading object like { parent: 'A', value: 'B' } passed
validation but the serializer always uses parent and silently discarded value.
Add a refine rejecting the ambiguous case at the boundary. Adds a route test.

Round 5 (Cursor + Greptile):
- cascading scalars must be non-empty (min 1), matching option/userpicker, so
  '', [''], { parent: '' } are rejected at the boundary instead of passing
  validation and then being silently dropped by the serializer.
- reject a cascading entry that sets child both at the top level and inside
  value (the serializer would keep one and discard the other). Adds route tests.

Completes the round-5 conflicting-child refine, which only checked the object
form of value.child. A [parent, child] array plus a top-level child now also
rejects at the boundary (nested child is value[1] for the array form). Adds a
route test for the array case.

Round 7 (Cursor):
- customFields tool param was type: 'json', which the schema builder exposes to
  LLMs as a JSON Schema object while the contract requires an array — a model
  emitting an object/map would 400. Switch to type: 'array' with an items schema
  describing { fieldId, type, value }, matching the array params in jira/write.ts.
- text custom-field values must be non-empty (min 1), so '' is rejected at the
  boundary instead of passing validation and being silently skipped — consistent
  with select/userpicker/cascading. Adds a route test.