[P2] Action-param value-shape parity net: assert every FORM_FIELD_TYPES param round-trips to the endpoint contract #2714

Why

Since #2700 / ADR-0059, ActionParamDialog routes every param through the shared form field-widget renderer (paramToField() → getLazyFieldWidget). That was the whole win — but it also means each param now emits its widget's own value shape, and those shapes differ:

• date/datetime/time → ISO-ish strings
• number → number (not string)
• boolean → boolean
• select → string; select + multiple → string[] (new in feat(fields): select+multiple → multi-value chip picker; restore fields/core lint gates #2709)
• lookup/user → id string or string[]
• file/image → an upload descriptor object {name, url, size, mime_type, …} (or an array) — not a fileId string

#2700's acceptance list explicitly called for value-shape parity coverage ("confirm each round-trips to what the action runner/endpoint expects; add coverage"), but no test net pins it today. Without one, a future widget swap can silently change a param's emitted shape and break an endpoint's input contract with no failing test.

Scope

• A table/test net (mirroring the paramToField drift test's style) asserting, for each FORM_FIELD_TYPES type usable as a param, the shape the dialog emits on confirm (primitive vs. object vs. array; multiple → array).
• Pin the known contracts that endpoints rely on: number→number, boolean→boolean, date→string, select→string, select+multiple→string[], lookup→id(s).
• Document the emitted-shape table (README / ADR-0059 addendum) so param authors know what a type:'X' param will POST.

Explicitly out of scope (owned elsewhere)

• The file/image → fileId value-shape gap and its serialization at the param boundary is owned by [P2] approvals: declare attachments on approve/reject and retire the inbox's hardcoded composer #2698 (Phase 1) — reference it, don't duplicate. This issue covers the general net for the non-upload types and the overall contract table; it should adopt whatever file serialization [P2] approvals: declare attachments on approve/reject and retire the inbox's hardcoded composer #2698 lands.

Acceptance

• A test fails if any param type's emitted value shape changes unexpectedly.
• The emitted-shape contract is documented.

Refs

• [P3] SDUI: render ActionParamDialog params through the shared form field-widget renderer (retire bespoke per-type branches) #2700 / feat(app-shell): render ActionParamDialog params through the shared form field-widget renderer (#2700, ADR-0059) #2704 / ADR-0059 (shared-widget param rendering; the acceptance item this closes) · fix(app-shell): guard ActionParamDialog submit during file upload + map spec autonumber (ADR-0059 follow-ups) #2707 (upload guard) · feat(fields): select+multiple → multi-value chip picker; restore fields/core lint gates #2709 (select+multiple → string[]) · [P2] approvals: declare attachments on approve/reject and retire the inbox's hardcoded composer #2698 (owns the file fileId serialization — Phase 1)