fix(tui): clarify optional LiteLLM custom endpoint

[aidandaly24]

Description

Clarify the optional LiteLLM endpoint field in the TUI.

• Rename API base URL to Custom API base URL in the project create/add Harness model step, imperative Harness create/update wizard, and project review summary.
• Explain that leaving it blank uses the model provider's default endpoint.
• Update nearby screen assertions, including the compact 80x24 layout check.

The field remains optional. Model configuration, endpoint resolution, and request payloads are unchanged: LiteLLM can route directly to the provider encoded in the model ID, while a custom API base overrides that destination.

Related Issue

Addresses the LiteLLM endpoint optionality feedback from the CLI v1 UX review, item 10. No standalone GitHub issue was created for this copy-only follow-up.

Documentation PR

Not applicable. The explanation is included in the TUI. No flags or command descriptions changed, so command.md is unchanged.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

How have you tested the change?

• I ran bun test: 3,975 passed, 0 failed, 6 snapshots. The initial command-sandbox run hit subprocess/loopback restrictions; the full rerun through the TUI-harness runner exited 0.
• I ran the relevant end-to-end tests with bun run test:e2e, or explained why they are not applicable: AWS E2E tests are not applicable to this copy-only change. No deployment or model invocation was performed.
• I ran bun run typecheck
• I ran bun run lint:check
• I ran bun run format:check
• I ran bun run build
• If I modified src/assets/, I updated affected snapshots with bun test <test-file> --update-snapshots and committed them (not applicable; no asset changes)

Also tested the actual packaged Node CLI through tui-harness, with PNG screenshots captured and visually inspected:

• Project create at 80x24: the full renamed label, help, and focused input fit without footer overlap; blank URL advances to review and omits the endpoint summary.
• Project create at 100x34: a custom URL is editable and appears under Custom API base URL in review.
• Imperative Harness create at 100x34: the renamed field/help are readable and blank URL advances to memory configuration.

All flows were stopped before creation confirmation. No AWS resources or project directories were created.

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published (no dependent changes)

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[agentcore-devx-automation]

AgentCore Harness Review

Verdict: Looks good

This is a focused copy change renaming the LiteLLM endpoint field from "API base URL" to "Custom API base URL" with clarified help text ("optional · leave blank to use the model provider's default endpoint"). Both occurrences in HarnessWizard.tsx and HarnessModelField.tsx (including the harnessModelSummary output label) are updated consistently, and the three affected test files are updated to match — including positive assertions for the new help text so regressions in the clarification will be caught.

A quick grep confirms there are no lingering references to the old "API base URL" label anywhere in src/, and the programmatic identifiers (apiBase, --api-base, schema field) are intentionally left unchanged. No telemetry or test-structure concerns apply to a wording change like this.

LGTM. 🚀

[agentcore-devx-automation]

Claude Security Review: no high-confidence findings. (run)

[notgitika]

CI failing because this is built from a stale branch. The issue is fixed on refactor head