fix: set Kind discriminator in ToLegacyTask A2A conversion

[Daniel-Vaz]

Description

Fix Pydantic validation error when resuming tasks after ask_user HITL interrupt.

Problem

When converting A2A v1 tasks back to legacy v0 format in ToLegacyTask(), the Kind discriminator field was not being set. This caused tasks serialized through the Go controller to be rejected by Python's Pydantic validation with:

ValidationError: 1 validation error for KAgentTaskResponse
data.kind
  Input should be 'task' [type=literal_error, input_value='', input_type=str]

Solution

Add Kind: trpc.KindTask to the trpc.Task struct literal in ToLegacyTask(), matching the pattern already used by toLegacyMessage().

Changes

• convert.go: Set Kind field in legacy task conversion
• convert_test.go: Add regression assertion in assertBackwardTaskFixture()

Testing

• All existing tests pass
• New assertion prevents future regressions

Fixes #2037

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[Daniel-Vaz]

Build error doesn't seem related with the change:

ERROR: process "/bin/sh -c mkdir -p /opt &&     cd /opt &&     git clone --depth 1 --revision=ef4afdef4d711ba21a507d7f7369e305f7d3dbfa https://github.com/anthropic-experimental/sandbox-runtime.git &&     cd sandbox-runtime &&     npm install --save-exact lodash-es@4.18.1 @types/lodash-es@4.17.12 &&     npm install --save-exact brace-expansion@5.0.6 &&     npm run build &&     npm prune --omit=dev &&     npm install -g --ignore-scripts" did not complete successfully: exit code: 132

[Daniel-Vaz]

Using version 0.9.8 of the controller:

Questions were answered but there is no further reaction in the UI, checking the Agent logs I see the error logs describe in the issue #2037

---

Using a locally built version with the changes suggested in this PR

[jmhbh]

makes sense to me, LGTM