fix: keep macOS proc-macro dylibs loadable

[tag-und-nacht]

On macOS 27.0 (Apple Silicon) with Rust 1.96.1, cargo xtask fresh-build --release failed while compiling strum with E0463 for strum_macros.

The underlying loader diagnostic was:
dlopen(.../libstrum_macros-*.dylib): mis-aligned LINKEDIT string pool

Cargo profile stripping was producing malformed proc-macro dylibs. Keep stripping disabled for release artifacts and optimized dev/build dependency overrides; debug = false still avoids embedding debug info.

Verification:

• Exact CPATH/LIBRARY_PATH + cargo xtask fresh-build --release: passed
• Full release compile and fresh Lisp generation/byte-compilation: passed
• cargo test -p xtask: proc-macro compilation passed; 118/125 tests passed, with 7 pre-existing CI-contract/fixture failures unrelated to this change
• git diff --check: passed

[tag-und-nacht]

Note: Nix does not currently avoid this: it pins the same Rust 1.96.1 toolchain and does not pin a macOS SDK/linker. The host Apple linker may still be used inside nix develop, so the fix benefits both Nix and non-Nix builds.

[eval-exec]

Thank you

[tag-und-nacht]

@eval-exec This issue is relevant for macOS users: rust-lang/rust#157750