[codex] Preserve enabled local features during wrapper updates

[avifenesh]

Summary

• stage enabled linux-features/local/<id> directories into fetched wrapper sources before wrapper rebuilds
• apply the same preservation path to packaged rebuilds and user-local helper managed checkouts
• keep upstream top-level feature ids authoritative, so a future built-in feature is not duplicated as local

Root Cause

Wrapper updates rebuild from a freshly fetched wrapper source. If the current install had an enabled local Linux feature, the saved feature config still referenced that id, but the fetched source did not contain linux-features/local/<id>. scripts/lib/linux-features.js then rejected the enabled id and the wrapper update stayed pending.

Validation

• cargo fmt --all --check
• bash -n contrib/user-local-install/files/.local/lib/codex-desktop-linux/common.sh tests/scripts_smoke.sh
• git diff --check
• cargo test -p codex-update-manager wrapper_apply
• bash tests/scripts_smoke.sh
• cargo clippy -p codex-update-manager --all-targets -- -D warnings
• cargo test -p codex-update-manager

[ilysenko]

Reviewed current head 9a9c0ba. No blockers found. Verified GitHub checks are green and local focused updater/user-local tests pass, including the full scripts smoke suite.