[Improve] Guide kickoff messages to end with a period

[roomote-roomote]

Opened on behalf of Matt Rubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

Related issue

N/A — follow-up after #353 still left kickoff messages without trailing punctuation in practice.

Why this PR exists

• A maintainer explicitly invited this PR in the linked issue or discussion
• I am a maintainer / this is internal Roomote work

What changed

Prompt-only guidance plus eval coverage so router kickoffs are short complete sentences ending with a period.

• Reword the kickoff section to ask for a complete sentence ending with a period
• Update examples to include trailing periods
• Align the structured-output field description and router eval contract
• Add hasValidKickoffMessage to the router eval assertions (non-empty + trailing period)
• Apply that assertion on representative basic and model-routing cases
• Enable the production kickoff section in the Promptfoo eval prompt via includeKickoffMessage: true
• Require a non-null kickoffMessage string in the eval output format

No runtime force-normalization or static-template punctuation changes.

How it was tested

Pre-push lint:fast, check-types:fast, and knip passed. Full pnpm eval:router was not run in this environment (needs live LLM provider keys); the assertion and prompt flags are wired into the existing Promptfoo suite.

Checklist

• The PR title follows the repo convention: [Fix], [Feat], [Improve], [Refactor], [Docs], or [Chore] followed by a user-facing description
• This PR is small and scoped to one change
• pnpm lint and pnpm check-types pass locally
• I added tests or included a clear manual validation note above
• I removed secrets, tokens, private keys, and customer data from code, logs, and screenshots
• If this change should appear in the changelog, I ran pnpm changeset

Impact

Router prompt + schema encourage sentence-ending periods on dynamic kickoffs, and the router eval suite regresses that contract with the production kickoff section enabled.

[roomote-roomote]

No code issues found. See task

• packages/cloud-agents/evals/router/prompts/routing.ts:152 (Low) The router eval suite does not inspect kickoffMessage, so it passes when the model omits it or returns text without a trailing period. Add a kickoff assertion and apply it to representative router cases so this prompt contract is regression-tested.
• packages/cloud-agents/evals/router/datasets/basic.yaml:31 (Medium) The newly required assertion runs against the Promptfoo prompt built at routing.ts:163 without includeKickoffMessage: true; that prompt omits the production kickoff section, while its output contract still explicitly permits kickoffMessage: null. The eval can therefore fail even when the evaluated prompt follows its own contract. Enable the kickoff section for this suite and make the eval output field required/non-null.

_{Reviewed 23c4023}

[roomote-roomote]

Addressed the remaining open review item in 23c4023:

• Eval prompt now builds with includeKickoffMessage: true (production kickoff section enabled)
• Eval output format requires non-null kickoffMessage string ending with a period

Previous item (assert + representative cases) remains in 057c836.