[Kinflou]

Documents stage 2, rollout steps 1-3, of the shared runtime core (runtime#49-#53, #55-#57, #59, #60, simulator#29). Documentation only.

Changes

• proposals/shared-runtime-core/core-interface.md
  • Status is now accepted, with steps 1-3 done. New "What's built" lists the PRs.
  • New "What changed from the proposal", each item checked against origin/main: method names (runtime#45), Call unchanged, COMLINE_ERR_BUSY (23), exact BUFFER_TOO_SMALL sizes, the frame-limit design, one envelope-based encode_reply, one-way by mode and connection framings only, which fields each framing reads, JSON-RPC without std confirmed, and the deferrals (comline_connection_size/init after 1.0, comline@2 before 1.0).
  • Stale lines fixed: the C API sketch is replaced by a pointer to the reference, the crate layout, the "What changes in the core" table (now with status), the toolchain note, the JS glue's panic handling and memory use, the open questions, the rollout.
  • Bindings (stage 4), ABI 1.0 and the release workflow stay as future work.
• reference/c-abi.md (new, in the nav under Reference): ABI version, status codes, constants, the four structs, every function with its errors, what each framing reads, frame limits, the implementation rules, wasm32 and the JS glue, building, how it is verified, and the measured crossing cost.
• proposals/shared-runtime-core/verification.md: the FFI vector harnesses, ffi_feed and ffi_vs_core, the differential proptest, stream_split, the FFI benches and the gate over every target; runtime#58 (deferred) and its exemption under "Found along the way".
• proposals/shared-runtime-core/index.md, proposals/index.md: stage 2's status.

Where numbers come from

• Crossing cost: the published rust.bench.json on runtime's reports branch, main at cb41d31 (the merge of runtime#60), which has the ffi/abi/* and ffi/core/* ids. The PR Packet dispatch: transitions, replies and two-way request ids decided #60 body's local figures (e.g. encode_request 965 to 742) are cited separately, as local.
• 65 vector cases: counted from the six vector files the ABI carries (8 + 9 + 8 + 9 + 12 + 19).
• Nightly fuzz figures: rust.fuzz.json on reports, main at b773057.
• Everything else is from runtime/ffi/include/comline.h, runtime/ffi/src/lib.rs, runtime/core, the workflows and the PR bodies.

Checked

• zensical build --strict (as docs.yml runs it, after sync-language-support.py --render-reports): no issues. No unrendered {{ or {% in the built site. Every link and anchor on the changed pages resolves.
• The CLI, IDL and language-support drift workflows are path-filtered and none of these paths is in them.