forms(qml): a host slot can draw a nested-object member, and the form encodes it member by member

[Yaraslaut]

What / why

A struct member (IgnitionSpecimen specimen, std::optional<PycnometerDetermination> determination1) has no built-in control: DynamicForm flattens it to one text field and reports it unrepresentable, so a form carrying one never becomes ready. #809 gave a host slot a way to draw a std::vector<Row> member. This PR does the same for a nested object, following #809's approach.

An object member no slot claims behaves exactly as before. tst_DynamicFormNestedAggregate.qml is untouched and green.

Contract

Where	Name	Meaning
descriptor	isObject	Object schema with properties that no typed control claims (a Quantity/Choice is not one). kind stays "object".
descriptor	objectFields	The member descriptors, in x-order. Recursive: an object member carries its own objectFields and a collection member its itemFields. Bounded by maxObjectDepth (4); a $defs type is never described twice on one path, which makes it cycle-safe.
descriptor	claimedBySlot	A registered slot resolves for this top-level member, so unrepresentable is "" for it and for every object or collection described inside it.
slot (optional)	objectValue	Binding to the value as {member: cellText | nestedValue} ({} when blank).
slot (optional)	setObject(value)	Same as setValue(JSON.stringify(value)).

Encoding rules (encodeObjectValue):

• Each leaf goes through encodeFieldText, the encoder the member would get at top level: same locale normalisation, precision limit and bounds.
• A nested object is encoded recursively. A collection inside the object reuses the forms(qml): a host slot can draw a std::vector<Row> member, and the form encodes its rows #809 row encoder.
• A blank optional leaf is omitted. A blank optional object (absent, {}, or every member blank) is also omitted.
• A blank required leaf or required object gives null, so the form is not ready. The same happens for a value that is not an object and for a cell that does not encode.

Prefill: prefill / prefillFromJson decode a stored object with decodeObjectValue, the inverse of the encoder, member by member through decodeFieldValue. So prefill → submit round-trips.

Schema-side fix included (include/morph/forms/forms.hpp). recurseIntoNestedAggregateIfAny did not look inside std::optional<Sub>, which glaze emits as anyOf: [<Sub>, {type: null}]. As a result, an optional sub-record's members got no x-order, title or required, and none of their FieldMeta (ExtUnits, x-displayDecimals, label). It now recurses into the non-null branch, and that also covers an optional std::vector<Sub>.

Tests

• New src/qt/forms/tests/tst_DynamicFormObjectSlot.qml, 24 cases, with assertions on the submitted body. It covers:
  • descriptor shape: depth 2, units, decimals and labels from nested FieldMeta, a self-referential type stopping, and byKind("object")
  • claimed → representable
  • exact bodies for BinderIgnitionSection and MaxDensitySection
  • blank-optional omission, and required-blank → not ready
  • de_DE comma cells
  • row vectors inside the object
  • the prefill round trip, in C and de_DE
  • the unclaimed case staying unrepresentable
• 3 new tests/test_nested_forms.cpp cases: a required nested member's FieldMeta, and a depth-2 optional member in both the $ref and the inline anyOf form.

Mutation checks (actually run):

Break	Red
Leaf encoder in encodeObjectValue replaced by plain string quoting	9 of 24 QML cases (all in the new file; 410/419 suite-wide)
forms.hpp optional recursion reverted	2 of the 3 new C++ cases (9 assertions)

Local results: MSVC 14.5x, Qt 6.11.1, QT_QPA_PLATFORM=offscreen:

• forms_qml_logic 419 passed, 0 failed
• ctest -R forms 10/10
• full ctest 1596/1596

Out of scope

• An object or collection inside a row of a claimed std::vector<Row> is still unrepresentable, because row cells are texts.
• Nested cells use the canonical unit only. There is no unit selector per cell.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 83.33333% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
include/morph/forms/forms.hpp	83.33%	0 Missing and 1 partial ⚠️

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