fix: preserve aliases from memoryrefget

[MilesCranmerBot]

Registers Core.memoryrefget as returning an alias of its memory reference argument. Without this, repeated outer[1] array element extraction is treated as fresh values and misses aliasing violations.

Adds the E1 regression from the Claude experiment branch through the public @safe path.

Tested:

• BORROWCHECKER_ONLY_AUTO=true BORROWCHECKER_TESTITEM="Auto @safe" julia --project=. -e 'using Pkg; Pkg.test()'

[MilesCranmer]

@MilesCranmerBot can you make another PR that makes the nightly tests not fail the CI? allow-fail or whatever

[MilesCranmerBot]

Opened #76.

Change: the nightly Julia setup/build/test steps now soft-fail at the step level, so nightly-ubuntu-x64 should stop reporting a failed check run. The prior job-level continue-on-error made the workflow green but still left that individual check red.

Commit: MilesCranmerBot/BorrowChecker.jl@902cdd4
Verification: git diff --check; Ruby YAML parse of .github/workflows/CI.yml. New PR checks are running.