A tool's `inputSchema` may carry composition keywords at its root — the
2026-07-28 revision makes this explicit — but both form builders enumerate
the root's `properties` and nothing else. A schema keeping its fields on
`allOf`/`oneOf`/`anyOf` branches therefore rendered no controls at all: no
branch picker, no fields, not even the raw-JSON fallback a union-typed
*property* falls back to, so the tool could only be called with empty
arguments.
Adds `core/json/rootUnion.ts`, one flattening shared by all three clients so
they cannot drift on which schemas they can render:
- `allOf` is merged unconditionally (conjunctive — there is no choice to
present), a root `oneOf`/`anyOf` is returned as branches.
- Web `SchemaForm` renders a Variant picker above the fields and prunes the
outgoing branch's values on a switch, since they are no longer visible and
would describe a shape the call is not making.
- TUI `schemaToForm` gives each branch its own section with optional fields —
ink-form is static, and only one alternative applies to a call.
- `convertToolParameters` looks through the branches, so a CLI `--tool-arg`
is typed by the schema that declares it rather than sent as a string.
Required-field gating asks whether *any* branch is satisfied, which is
selection-independent and never blocks arguments the schema accepts. A
`const` is seeded like a `default` and rendered read-only: it admits exactly
one value, so anything else the user could type produces a rejected call.
Adds a `root-union-schemas-http.json` showcase server.
Closes#2123
Signed-off-by: cliffhall <cliff@futurescale.com>
5933162dd0