fix(trace): args rides the tape as a nondeterminism source (#471)

[InauguralPhysicist]

What

builtin_args returned argv directly, unwrapped — the last un-taped nondeterminism source reachable by a pure script, and a hole in the closed-world invariant behind deterministic replay. A program that branches on args recorded a tape under one invocation and silently diverged when replayed under a different argv. This is the exact class the #408 task layer's chaos-mode --seed N scheduling would hit (seeds arrive via CLI, liferaft's --seed N pattern).

Fix

The recorded argument list now rides the tape as one N record; replay serves it regardless of the live argv.

Because args builds its list before returning, it uses the TRACE_NONDET_TAKE / TRACE_NONDET_RECORD pair rather than TRACE_NONDET_RET — under replay the early TAKE short-circuits before the list is built, so the live construction is neither run nor leaked (the abandoned-value trap the extend-vm checklist warns about). The tape already round-trips a list of strings (parse_value_p, src/trace.c:868), so no serialization work was needed.

Verification

• tests/test_replay.sh: record under A B, replay the same script under X Y Z, assert the recorded args win — plus a live (no-replay) run under X Y Z that prints ["X", "Y", "Z"], proving the tape actually overrides rather than coincidentally matching.
• Manual: EIGS_TRACE → N args=["A", "B"]; EIGS_REPLAY under X Y Z → ["A", "B"].
• Full suite green release AND ASan (detect_leaks=1): 2689/2689, 0 failed, no leak-tally increase.

Docs

• docs/TRACE.md: new Process category listing args, and a note that value-building builtins use the TAKE/RECORD pair.
• CHANGELOG.md: entry under [Unreleased] → Fixed.

Closes #471

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