fix(docs): build docs.rs with an engine feature

[butterflyfish]

Summary

GitHub Publish Packages succeeded. docs.rs failed for rong_crypto 0.6.0: rustdoc ran with no engine feature, so rong::JSContext / JSValue were cfg'd out.

That turned out not to be a crypto problem. No crate in the repo had [package.metadata.docs.rs], and every module crate hides its public API behind an engine feature, so the same failure is waiting for all of them. Checking docs.rs directly: 14 crates are red, and only rong, rong_core and rong_rt are green.

rong           OK  0.6.0        rong_url       RED 0.6.0
rong_core      OK  0.6.1        rong_buffer    RED 0.6.0
rong_rt        OK  0.6.1        rong_encoding  RED 0.6.0
                                rong_console   RED 0.6.0
rong_crypto    RED 0.6.0        rong_stream    RED 0.6.0
rong_http      RED 0.6.1        rong_timer     RED 0.6.0
rong_abort     RED 0.6.1        rong_event     RED 0.6.0
rong_redis     RED 0.6.0        rong_exception RED 0.6.0
rong_s3        RED 0.6.0        rong_modules   RED 0.6.1

What

• [package.metadata.docs.rs] features = ["quickjs"] on all 14 — the same requirement as cargo publish --features quickjs.
• rong_crypto 0.6.0 → 0.6.1 so its page rebuilds (0.6.0 cannot be fixed in place).

Each of the other twelve was verified to build its docs under quickjs alone — cargo doc --no-deps -p <crate> --features quickjs, all OK — so none needs a different or additional feature.

The version bumps are deliberately not here

docs.rs cannot rebuild a version in place, so a red page only turns green when that crate next publishes. Turning the other twelve green now would mean patch-bumping and republishing twelve crates, which is a release decision and belongs in the chore(release) commit, not in a fix PR. What has to happen first is the metadata, so that whenever each one next ships, it ships with working docs.

Worth deciding as part of the next release wave: bump and republish the twelve to clear the backlog in one go, or let them turn green individually as they change.

After merge

Publish Packages from master: package_scope=rust, rust_selection=--crate rong_crypto, package_tags=always.

Validation

• cargo doc --no-deps -p <crate> --features quickjs for all 14
• cargo metadata parses every manifest
• Relied on GitHub Actions host CI for platform coverage