feat: enhance output validator with error handling and schema support

[Z-M-Huang]

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[Z-M-Huang]

GitVibe Review Matrix

Status: completed
Next state: changes-required

Synthesized 3 successful role reviews for PR #5 and performed an additional diff inspection. One regression needs a fix before approval: discriminator auto-enabling can turn previously valid schemas into invalid configured schemas.

Next Action

Continue with changes-required.

Result

When present, required fixes are posted as pull request review comments. Full structured output remains in the workflow run summary.
Workflow run: https://github.com/markhuangai/agentool/actions/runs/26477105606

Inline comments: 1

Required Fixes

1. src/output-validator/index.ts:192 unconditionally adds discriminator: true whenever hasOneOfDiscriminator(config.schema) is true. Ajv documents that discriminator mode is not enabled by default and that compile fails when its limitations are not met, including unsupported mapping, missing required discriminator property, non-inline/non-direct-$ref branches, or non-unique const/enum tag values. Because the pre-PR Ajv config used strict: false without discriminator mode, those schemas could compile and validate through normal oneOf; this PR can now return Error [output-validator]: Invalid configured schema for every call. Fix by only enabling discriminator mode for schemas that satisfy Ajv's discriminator constraints, or by retrying compilation without discriminator mode when discriminator compilation fails.

[Z-M-Huang]

This enables Ajv discriminator mode for any schema that merely has discriminator.propertyName next to oneOf. Ajv discriminator mode has additional compile-time constraints, so schemas that previously compiled with normal oneOf validation can now become invalid configured schemas. Please add compatibility checks or fall back to a non-discriminator compile when discriminator compilation fails.

[Z-M-Huang]

GitVibe Review Matrix

Status: completed
Next state: review-passed

Synthesized 3/3 successful role reviews for PR #5 and re-inspected the follow-up diff. The prior discriminator auto-enable regression is addressed by a fallback compile path, and no blocking correctness, security, regression, test, or maintainability issues remain.

Next Action

Continue with review-passed.

Result

When present, required fixes are posted as pull request review comments. Full structured output remains in the workflow run summary.
Workflow run: https://github.com/markhuangai/agentool/actions/runs/26480711312