[Kinflou]

Moves generation to core 1669a2fe4dbc5592a96a2964d7ae13e985b76701 (core master after ComlineProject/core#240, which follows #239) and takes the one kernel path change from #128.

• codegen/Cargo.toml: comline-core (dependency and dev-dependency) b933209 -> 1669a2f.
• conformance/Cargo.toml: comline-core b933209 -> 1669a2f.
• codegen/src/protocol.rs: the doc comment on the framing type named comline_runtime::framing::Datagram2Framing, which never existed at that path; it is comline_runtime::contract::Datagram2Framing.

No other change is needed for core#239: the doc renderers read the @unverified reason from the doc model, not from unverified::protocols(). Cargo.lock is untracked here, so no lockfile change.

References #128 without closing it: the regenerated goldens (conformance/tests/golden/connections_async/rust/{conformance,connection}.rs, handshake_comline2/rust/connection.rs) come after comline-rust emits the new paths. Part of ComlineProject/runtime#111.

Known: conformance does not build in this PR, by design

comline-conformance dev-depends on comline-codegen-rust (comline-rust de0b8e5) and comline-codegen-typescript (comline-typescript 9952c5a). Both still pin core b933209, so cargo test at the workspace level resolves two copies of comline-core and fails inside those two crates, not in generation's code:

error[E0308]: arguments to this function are incorrect
   --> .../comline-typescript-.../9952c5a/codegen/src/generator.rs:129:45
129 |         collisions::check(namespace, units, derived_names(units, &req.schemas, &req.encodings))?;
note: expected `&[FrozenUnit]`, found `&Vec<FrozenUnit>`
note: there are multiple different versions of crate `comline_core` in the dependency graph
error: could not compile `comline-codegen-rust` (lib) due to 29 previous errors
error: could not compile `comline-codegen-typescript` (lib) due to 20 previous errors

cargo tree -d shows comline-core (and comline-core-stdlib) at both 1669a2f and b933209. Every error is E0308 or its note about multiple versions of comline_core; there is no other kind. This resolves once comline-rust and comline-typescript are bumped to core 1669a2f (which pins generation at this PR's merge) and this repo's conformance dev-deps are re-pinned at their tips, together with the golden regeneration. The same intermediate state occurred in the previous editions cascade (bb89a51, fixed by 311e6ae). So the "Cargo Build & Test" cargo test step is expected to be red on this PR.

Also known and left alone: lib-gen/lua and lib-gen/luau pin core aa84d97, and conformance/tests/golden/external_std/rust pins comline-rust e1b2167. They are unwired fixtures/stubs.

Tested locally (CI's commands)

• cargo build: OK.
• cargo test -p comline-codegen -p comline-doc-markdown -p comline-doc-html, all green: codegen 137 lib + 4 comline_toml_schema + 3 doc_model; doc-html 1 lib + 9 golden; doc-markdown 1 lib + 6 golden.
• cargo test for the workspace and -p comline-conformance: does not compile, for the reason above; no conformance tests ran.
• Not run locally: the wasm jobs (cargo build -p comline-codegen and the two renderers for wasm32) and the other-OS jobs.