Three Rust unit tests omit schema-required fields (connection, context) — 3 cargo test failures

[sethjuarez]

Summary

Three handwritten Rust unit tests build model payloads that omit fields the schema declares required. The generated loaders correctly reject them.

cargo test on wip/connection-open-discriminator against @typra/emitter@0.4.20:

test result: FAILED. 293 passed; 3 failed; 0 ignored

Same root pattern as #450, but in handwritten Rust test data rather than in vectors, so the fix locations are unrelated.

1 & 2. McpTool.connection — 2 failures

``
---- tool_dispatch::tests::test_dispatch_layer3_kind_handler stdout ----
panicked at prompty\src\model\tools\tool.rs:115:13:
connection: missing required field

---- tool_dispatch::tests::test_dispatch_layer3_wildcard_handler stdout ----
panicked at prompty\src\model\tools\tool.rs:115:13:
connection: missing required field
``

schema/model/tools/mcp.tsp:17 — connection: Connection;, required, no default.

runtime/rust/prompty/src/tool_dispatch.rs:

rust let agent = agent_with_tools(serde_json::json!([{ "name": "my_mcp_tool", "kind": "mcp", "serverName": "test-server" }]));

No connection. (It also omits approvalMode, which mcp.tsp:29 likewise declares required — that would fail next; see #450.)

3. ModelInvocationRequest.context — 1 failure

---- pipeline::live_turn::tests::streamed_responses_tool_round_preserves_delegated_continuation stdout ---- panicked at prompty\src\model\pipeline\model_invocation_request.rs:45:13: context: missing required field

schema/model/pipeline/invocation.tsp:119 — context: ModelInvocationContextSnapshot;, required, no default. The test payload in runtime/rust/prompty/src/pipeline/live_turn.rs omits it.

Both files are handwritten

Neither src/tool_dispatch.rs nor src/pipeline/live_turn.rs carries an auto-generated banner; the panic sites (src/model/tools/tool.rs, src/model/pipeline/model_invocation_request.rs) are generated, but they are being handed incomplete payloads by handwritten tests.

Suggested fix

Add the missing fields to the three test payloads — or, if these fields are genuinely meant to be optional, change the schema, in which case #450 should be resolved the same way and at the same time.

Not verified

I did not check whether the equivalent Go, TypeScript, Python or C# unit tests build the same payloads; those suites are green on these paths, so if they do construct them they are supplying the fields.

[sethjuarez]

Fixed on wip/typra-0.4.20-regen in de3e1809 (supply the schema-required fields) and 336d6c20 (reject a bare-string template, per template_string_invalid).