feat(config): add gate.readiness.minScore round-trip test hardening

[JSONbored]

The gate.readiness.minScore config field (src/signals/focus-manifest.ts:426) parses and serializes but lacks explicit boundary/branch tests for the round-trip and the score-clamp arms. Add focused tests so the parse↔gateConfigToJson round-trip and out-of-range warnings are branch-covered. Pure test hardening, no behavior change.

Deliverables

• Add unit tests exercising normalizeOptionalScore at the boundaries (min, max, out-of-range warn, non-number warn, null passthrough) for gate.readiness.minScore
• Add a parse→gateConfigToJson→parse round-trip test asserting readiness.minScore survives unchanged (src/signals/focus-manifest.ts:479)
• Assert the present flag flips correctly when only minScore is set
• Ensure 100% branch coverage on the readiness score arms

References

• src/signals/focus-manifest.ts:426 (readinessMinScore parse)
• src/signals/focus-manifest.ts:479 (readiness serialization)
• part of #1959 / #1681 (epic #1953)

Part of #1681.

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size: XS · gittensor:bug

[linear-code]

JSO-2170