Bump sigil-nrepl to 0.16.2

Phase 1 live-eval hardening (Codex, tasks/nrepl-phase-1-hardening):

• Structured error policy: default wire sessions return structured errors and stay in normal eval mode (agents/tooling never wedge in the debugger); debug-on-error is an explicit per-session opt-in with debug-state/frames/restarts/quit protocol ops.
• Expanded loopback regression suite (3 -> 13 tests): every advertised op, length-prefixed framing incl. partial-message reassembly, module context, live redefinition, error recovery, dynamic-import GET_CELL regression guard.
• macroexpand now runs under the request module context and restores it.

Interrupt/abort (item 1) and incremental output streaming (item 4) are deferred pending monorepo core primitives (t-40ce regvm preemptive yield, t-486d custom output-port); the abort prototype is recorded under notes/.