test: regression coverage for HAR/SCS #1030 fixes

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Description

Adds regression tests for merged #1030 fixes where silent failures were discovered during QA (search filters dropped, unresolved deep-link placeholders, compact stripping SCS marker rows).

Risky behavior now covered

• HAR list search: registry, artifact, artifact_version, and artifact_file list ops must send search_term on the wire (not a bogus search key).
• HAR artifact deep links: list items must resolve {artifactIdentifier} in openInHarness URLs.
• UPSTREAM registry create: config bodySchema documents required authType for UPSTREAM registries.
• SCS supply-chain links: artifact_security, scs_artifact_remediation, and scs_chain_of_custody deep links use {artifact} consistent with pathParams.artifact_id → artifact.
• List compaction: generic compactItems keeps _summary, _message, and _result marker objects from SCS extractors.

Test files added/updated

• tests/registry/registries-har-search-deeplinks.test.ts (new)
• tests/registry/scs.test.ts
• tests/utils/compact.test.ts

Why these tests materially reduce regression risk

Each failure mode was silent (filter ignored, placeholder left in UI links, agent guidance stripped). These dispatch-level and compaction tests fail loudly if query-param maps, pathParams, or ALWAYS_KEEP drift again.

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (test-only)

Checklist

• pnpm test passes (targeted: registries-har-search-deeplinks, scs deep-link block, compact markers)
• pnpm typecheck passes
• pnpm build passes
• pnpm standards:check passes
• pnpm docs:check passes