feat: establish free, token-efficient Agent search routing

[lennney]

Summary

• unify all 12 adapters across MCP, advanced search, CLI, and waterfall routing
• split result signals into relevance, normalized confidence, and independent source_count while preserving compatibility aliases
• add reproducible benchmark capture/replay with locked tokenizer, frozen fixture, execution telemetry, and a CI regression gate
• require Bearer authentication for HTTP MCP mode and enforce browser Origin allowlists
• harden zero-key fallback, stdio logging, CSDN SSRF handling, Node 18 compatibility, and Windows builds
• position the product around free + token-efficient Agent search, while retaining scoped historical 28.7% / 35.5% / 75% measurements

Verification

• build passed
• 510 Vitest tests passed across 43 files
• lint passed with no errors
• TypeScript check passed
• frozen benchmark verification passed
• GitHub Actions passed on Node 18/20/22 and Windows

Release note

No npm publish, tag, or version bump in this PR. Release preparation is deferred to next week.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Check the package version before skipping publish

With this new v* tag trigger, release tags now reach the publish job, but that job's check runs npm view <repo> "$VERSION"; npm view treats arguments after the package spec as fields ([<package-spec>] [<field>...]), not as the version to test. Once the npm package exists, this command can exit successfully even when $VERSION is unpublished, causing already_published=true and skipping npm publish for new tags. Use the package spec from package.json, e.g. agent-search-mcp@$VERSION, and query version instead.

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