refactor: extract Goal evidence helpers

[ByBrawe]

Summary

Continue the Goal modularization by extracting pure evidence/check/progress decision helpers from runtime/goal-runtime.js.

• add runtime/goal-evidence.js for concrete-evidence classification, configured-check status, completion-check requirements, progress snapshots, and meaningful-progress detection;
• keep goal-runtime.js focused on Goal selection/tool-argument normalization and lifecycle persistence mutations;
• preserve the existing source API by re-exporting all extracted helpers from goal-runtime.js;
• make goal-policy.js depend directly on the dedicated evidence module instead of the lifecycle facade;
• syntax-gate the new module while keeping the existing Goal runtime/policy regressions as compatibility coverage.

Behavior-preserving source modularization only. No runtime state schema or user-visible command behavior change. The committed single-file bundle is intentionally unchanged in this source-only slice; the Bundle Gate regenerated and exercised the exact source head on Linux and Windows.

Verification

Exact head a8256b7f58057b54483f3b6335c0bbaf620bf60f:

• CI: success on Linux/Windows, OpenCode 1.4.0/latest compatibility, and real OpenCode Loop hosts;
• Single-file Bundle Gate: success on Linux/Windows, including source regeneration, generated-entry import, real-host Loop/queued-Goal canaries, and generated-bundle regression suite;
• V2 Lifecycle Contract: success.

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