chore(release): v0.42.0 — ADR-7 path-H + multiply-instantiated + static-PIC + same-memory transcoding

[avrabe]

Cuts v0.42.0 — the full ADR-7 path-H arc plus two new fusion capabilities and
safety hardening. Everything below is already merged to main; this is the
version bump + CHANGELOG + SR release fields.

Highlights (since v0.41.3)

New capabilities

• Multiply-instantiated module support (RFC-46 Q1, --memory multi, SR-55) — feat(adr7): multiply-instantiated module support — RFC-46 Q1 (path-H inc 3) #362/test(adr7): memory+data-segment independence oracle for inc 3 — SR-55 verified #363
• Static-PIC data/element offset folding (bare + extended-const base + N) — feat(adr7): static-PIC data/element-offset fold — inc 4 (#353) #365/fix(353): fold extended-const (base+N) data/element offsets — completes inc-4 fold #368
• Same-memory string transcoding — feat(361): support same-memory string transcoding (lift the #360 hard-fail) #367

ADR-7 path-H architecture (pluggable per-boundary seams)

• Address-strategy seam (inc 1) — refactor(adr7): extract the address-strategy seam from the merger (path-H inc 1) #359
• Call-lowering + inline seam (inc 2) — refactor(adr7): extract the per-boundary call-lowering seam (path-H inc 2) #360
• ADR-7 decision record — docs(adr): ADR-7 — ABI & linking-strategy architecture (canonical mix-and-match vs symmetric/PIC fast lane) #354

Safety hardening

• Multiply-instantiated gated to the execution-verified MultiMemory case; SharedMemory/Auto reject (SR-31 'multiply-instantiated detection' is marked verified but the reject is dead code — multiply-instantiated modules fuse successfully on the live path (#362 wired it against its own commit message) #364) — fix(364): gate multiply-instantiated support to verified MultiMemory + fix SR-31 traceability #366
• Sync same-memory cross-encoding silent miscompile closed (refactor(adr7): extract the per-boundary call-lowering seam (path-H inc 2) #360/fuse: sync same-memory cross-encoding call skips transcoding — hard-failed in #360, support tracked here #361)

Falsification

• Multiply-instantiated sharing state between instances → multiply_instantiated_runtime fails.
• Un-folded static-PIC base + N offset → pic_extended_const_353 fails (wasmtime rejects).
• Same-memory UTF-8→UTF-16 skipping transcoding → adapter_safety::test_361_same_memory_utf8_to_utf16_transcoding returns the wrong sum.

rivet validate PASS; meld-core builds clean at 0.42.0.

After merge, tag v0.42.0 on the merge commit to trigger the release pipeline.

[github-actions]

LS-N verification gate

✅ 59/59 approved LS entries verified

	count
Passed (≥1 test, all green)	59
Failed (≥1 test failure)	0
Missing (no ls_*_NN_* test found)	0

_{Approved loss-scenarios.yaml entries are expected to have a
regression test named ls_<letter>_<num>_* (e.g. LS-A-11 →
ls_a_11_*). The gate runs each prefix via cargo test --lib --no-fail-fast and aggregates pass/fail/missing.}

Failed LS entries

(none)

Missing regression tests

(none)

_{Updated automatically by tools/post_verification_comment.py.
Source of truth: safety/stpa/loss-scenarios.yaml.}