Add Search API CLI commands

[chruffins]

Summary

• Add kernel search [query], search get <id>, and search providers [--slug] using the existing authenticated SDK transport and project scope.
• Support provider discovery, automatic or pinned routing, result limits, complete JSON requests from inline input/files/stdin, and preserved JSON responses.
• Disable automatic create retries to avoid duplicate billable searches.
• Add command help, README examples, and focused HTTP-level tests.

Scope and assumptions

• The merged Search API contract is authoritative; deferred content retrieval remains unavailable and is not exposed.
• Inline content and advanced strategies/options are passed through complete JSON requests with server-side validation.
• The pinned SDK does not expose a Search service, so this uses its generic Execute helper without dependency changes.
• JSON-only output preserves warnings, attempts, native fields, and large numbers. Search API access must be enabled for the organization.

Validation

• go test ./cmd -run TestSearch -count=1
• make test (go vet and full test suite)
• make build
• Search and provider command help smoke checks
• git diff main...HEAD --check
• No production API calls performed.

[cursor]

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