Add deterministic evaluation handoff bundle

[coreytshaffer]

Summary

• add tc eval build-handoff --fixture <jsonl> --actuals-dir <dir> --out-dir <new-dir>
• package validated fixtures and explicit actual outcomes into the fixed CR-123 handoff layout
• write a deterministic evaluation_handoff_manifest.v0 with sorted entries and SHA-256 digests
• preflight fixture and actual content with persistent privacy invariants before any output is created
• stage to a temporary sibling and atomically publish without overwrite or --force
• document the manifest contract and preserve external ownership of scoring

Why

CR-123 established the file-based evaluation handoff contract but deliberately did not materialize a bundle. CR-127 implements that bounded packaging step so operators can hand deterministic, inspectable static evidence to the external evaluator without adding scoring or evaluator execution inside TriageCore.

Impact

The builder requires explicit paths, copies source evidence byte-for-byte, rejects malformed, unsafe, unknown, sensitive, overlapping, or ambiguous inputs with closed reason codes, and leaves no final bundle after failure. Missing actuals remain allowed because the external evaluator—not TriageCore—owns pass/fail judgment.

Boundaries

No scoring, matching, verdicts, certification, evaluator execution/import, model/backend/network calls, routing, ledger, worker, approval behavior, automatic discovery, default paths, overwrite, compression, signing, upload, or publication is added.

Validation

• focused eval/bundle regression surface — 60 passed
• python -m pytest -q — 971 passed, 2 skipped
• python -m triage_core.tc_cli audit --privacy-invariants — 698 records passed
• git diff --check — clean