feat(providers): add CLOVA Studio embedding v2

[backryun]

Summary

• register Naver CLOVA Studio embedding v2 as a 1024-dimensional embedding model
• adapt the native one-text-per-request contract to OpenAI /v1/embeddings with sequential batch fan-out, stable indexes, and aggregated usage
• reject unsupported token-array, base64-encoding, and non-1024-dimension requests instead of silently changing their meaning
• treat malformed or HTTP-200 CLOVA error envelopes as provider failures

Validation

• node --import tsx/esm --test — 66 focused embedding tests passed
• npm run test:vitest — 50 files / 463 tests passed
• npm run typecheck:core
• node scripts/check/check-api-typecheck.mjs
• scoped ESLint for all changed files
• provider consistency and known-symbol gates with isolated storage

npm run lint currently exits 2 on both this branch and the unchanged base because the repository has stale suppression entries; the changed files themselves pass ESLint.

[backryun]

Superseded by #12277. CLOVA Embedding v2 has been absorbed into the unified CLOVA Studio modernization commit fcc2423, together with the Chat Completions v3 work and its regression coverage.

[diegosouzapw]

Validated in local merge-train on 192.168.0.113 — train of #12258 #12262 #12166 #12281 #11259 #11950 merged clean onto origin/release/v3.8.51 (f5e7095):

• Run 1 (/opt/actions-runner-omniroute-5, train tip 85cd9119): typecheck:core, file-size, complexity ×2, changelog-integrity — all green; the test:unit step was killed by a CI job landing on that runner mid-train (workspace clobbered — infra, documented risk).
• Run 2 (/srv/omniroute-train/.claude/worktrees/mt-green1, same 6 PRs re-boarded, fresh npm ci): unit 35768/35805 pass (/tmp/mt-unit2.log), vitest 464/465 (/tmp/mt-vitest2.log).
• Every failure is a latency/timing assert (bounded-time, event-loop lag, cooldown windows) on a box that was never idle (3 active CI runner workers throughout). Discriminated per merge-gates §3: the 3 persistent titles reproduce identically on the pure base tip on the same box (/tmp/mt-base-isolated.log, BASE_ISOLATED_EXIT=1 — same tests, same asserts), 5 more titles reproduce on the pure base on the devbox, and the single vitest failure (provider-family-combos) also fails on main's nightly without any of these PRs. Inherited/infra — not introduced by this train.