State predicates asserted in only one polarity (mutation survivors)

[leynos]

Context

From the first full mutation-testing run (ADR-007 workflow, 2026-07-04, partial). A cluster of state predicates is only ever asserted in one polarity, so forcing them to a constant survives the suite.

Surviving mutants

• src/connection/state.rs:70 — replace ActorState::is_shutting_down -> bool with false (the true mutant times out; the false mutant survives). Used in production at src/connection/mod.rs:314-315 to gate availability snapshot flags, yet tests/connection.rs only asserts !is_shutting_down or branches on it — never asserts it is true during shutdown.
• src/client/response_stream.rs:104 — replace is_terminated -> bool with true. src/client/tests/streaming.rs asserts is_terminated() == true after the terminator only; nothing asserts !is_terminated() mid-stream.
• src/app/envelope.rs:129 — replace Packet::is_stream_terminator -> bool with true (default method). The real impl Packet for Envelope does not override it, so the default false is production behaviour, but all terminator tests use types that override the method.
• src/connection/multi_packet.rs:82 — replace MultiPacketContext::is_stamping_enabled -> bool with true. With stamping disabled the mutant clobbers a pre-set correlation id via set_correlation_id(None) instead of leaving the frame untouched; tests/correlation_id.rs only covers enabled stamping.

Suggested tests

1. Drive a shutdown and assert snapshot.is_shutting_down == true within the shutting-down window.
2. After a data frame but before the terminator, assert !stream.is_terminated().
3. Assert a plain Envelope reports is_stream_terminator() == false.
4. Send a multi-packet frame carrying a pre-existing correlation id with stamping disabled and assert the id is preserved.

[coderabbitai]

🔗 Related PRs

#514 - Verify and fix documented code issues; Whitaker lint CI and docs [closed]
#527 - Add wireframe-verification crate with placeholder Stateright model (15.1.2) [closed]
leynos/podbot#90 - Plan ACP runtime method denylist enforcement (2.6.2) [closed]
#528 - Implement WireframeError error integration (#513) [closed]
leynos/rstest-bdd#496 - Surface GPUI scenario names on panic (10.1.4) [closed]

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[leynos]

Reconciliation against the first complete full mutation-testing run (run 29074771985, 2026-07-10, main @ 94a5d44): every survivor listed here persists, at the same lines (no drift). Still actionable as written.