test: regression coverage for DBOPS, diagnose single-step guard, CCM filters

[cursor]

Description

Adds targeted regression tests for recently merged production paths that lacked validation or guard coverage.

Triggered by inspection of recent merges (#679 DBOPS changeset existence, #691 diagnose single-step mode, #617 CCM recommendation filters). PR #696 (schema auto-sync) is data-only; schema contract tests are deferred until that lands.

Risky behavior now covered

1. database_changeset_existence bodyBuilder ([feat]: [DBOPS-2684]: DBOPS changeset existence check API addition #679) — rejects missing/empty changeset_ids, >100 ids, non-string/blank entries; accepts changeSetIds camelCase alias and trims whitespace.
2. harness_diagnose single-step guard (feat: unify pipeline_summarizer into failure+success analyzer with RCA #691) — when step_id is present, include_all_step_logs is suppressed so callers stay in single-step mode.
3. CCM recommendation count/stats paired-filter guard (Add new tool for ccm recommendations filters #617) — costCategoryDTOs omitted when only cost_category is provided without cost_buckets.

Test files updated

• tests/registry/dbops.test.ts — 7 new cases
• tests/tools/diagnose/pipeline.test.ts — 1 new case
• tests/registry/registry.test.ts — 2 new cases

Why these reduce regression risk

• DBOPS: Input validation is the only gate before batch uniqueness checks; regressions send bad payloads or accept invalid ids.
• Diagnose: Single-step guard prevents wasted log fetches and mode confusion for agents summarizing one step from a URL with ?step=.
• CCM: Partial category filters caused API errors; count/stats share the list body-builder pattern but were untested.

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other — test coverage

Checklist

• pnpm test passes (targeted: 235 tests in 3 files)
• pnpm typecheck passes
• pnpm build passes
• pnpm standards:check passes
• pnpm docs:check passes (N/A — no registry changes)

  

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[thisrohangupta]

Closing after draft cleanup: the still-useful regression coverage is consolidated in retained #716 and the relevant focused drafts/fixes, so this branch no longer has a unique improvement worth keeping open.