feat(ddi)!: every form field in the codebook, standard DDI first (#153)

[jstet]

Closes #153. Part 3 of #155, after #151 (logic) and #152 (structure).

Breaking for DDI readers: the question hint moves from preQTxt to postQTxt (the layout agreed with qwacback on #153, tracked in qwacback#37).

Standard DDI wherever one fits

Field	DDI
hint	qstn/postQTxt, one per xml:lang. Grid members and select_multiple options now keep theirs.
note row before a question / grid or select_multiple shared text	qstn/preQTxt only; no longer joined with the hint
guidance_hint	qstn/ivuInstr, now also on select_multiple options
date / time	varFormat/@category="date" / "time"
integer	var/@dcml="0"
range start / end	valrng/range/@min / @max (registry defaults when not authored)
order	qstn/@seqNo, the position among the data questions (a select_multiple's options share it)
what relevant depends on	qstn/backward/@qstn, the IDs of the referenced var or varGrp

cdl: notes only where DDI 2.5 has no place

cdl:default, cdl:appearance, cdl:parameters (only what no element holds, e.g. step=5, randomize=true), a group's cdl:hint (per language), cdl:exclusive (codes, on the select_multiple's varGrp), and stdyDscr/notes type="cdl:setting" subject="style".

Guard

• registry/conventions/ddiFields.jsonld maps every field of src/instrument/types.ts to one of three things: a standard DDI element, a cdl: note, or a documented loss.
• tests/ts/unit/ddi/fields.test.ts fails when a field has no entry, or when the convention names a field that doesn't exist.
• Documented losses: calculation and other unlifted columns, a choice list's name, the or_other shorthand as such, and GroupItem.closed.

LimeSurvey: integer vs decimal

• xlsform2lstsv now writes LimeSurvey's num_value_int_only=1 for integer, and an N question with it reads back as integer.
• This fixes lstsv2xlsform's known loss 1, which is updated in its README.
• The TSV fixtures gain the column.

Checks

• vitest: 1254 passed, including the new fields.test.ts.
• pytest validation and codegen: 127 passed, 3 xfailed.
  • The XSD and Schematron checks pass on every snapshot with the new elements and attributes.
  • The known-invalid fixtures fail with the same errors as before.
  • The Schematron mutators now match <qstn responseDomainType="…" without the closing >, since seqNo follows it.
• The schematron-worker tests pass (gradle).
• npm run validate and the drift check are clean.

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