docs(WO86): the contributing-language intake guide

docs/contributing-language.md

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+# Contributing a language — the 2-YAML path
+
+Everything Interscript trains is **config-driven**: a language is two
+YAML files plus a held-out eval set — never a fork of the pipeline.
+This document is the complete onboarding; if you need something it
+doesn't say, that's a framework bug — file it, don't work around it.
+
+## What you bring
+
+| you have | you contribute |
+|---|---|
+| An authority document (BGN/PCGN, ALA-LC, ISO, national standard) | a **map**: `.isc` in
+[interscript/maps](https://github.com/interscript/interscript-maps) — deterministic, no model needed |
+| A corpus of (input → output) pairs with a license | a learned model through the recipe path below |
+| Both | both — the map is the deterministic layer, the model completes what the table underdetermines |
+
+## The two YAMLs (in [interscript-models](https://github.com/interscript/interscript-models))
+
+### 1. `corpora/<source>.yaml` — the pinned data
+
+```yaml
+id: mylang-dict
+task: transliteration
+sources:
+  - kind: bucket
+    id: Interscript/isx-training/run-NNN-mylang   # staged data
+    revision: run-NNN-mylang
+    license: CC-BY-SA-4.0        # SPDX code; LicenseRef-* blocks publish
+    mount: /data-my
+splits:
+  train: {path: train.jsonl, rows: 10000, sha256: <sha256 of the file>}
+  test: {path: test.jsonl, rows: 1000, sha256: <sha256>}
+```
+
+Laws: every row file is sha256-pinned; the license is an SPDX id or an
+explicit `license_review:` block (owner waiver); provenance goes in
+comments (who produced the data, from what upstream).
+
+### 2. `recipes/<lang>-<task>.yaml` — the training contract
+
+```yaml
+id: mylang-diac
+corpora:
+  train: mylang-dict@<revision>
+  test: mylang-dict@<revision>#test
+stages:
+  - name: sft
+    route: legacy:some_trainer_hf.py   # or a registered stage type
+    params: {EPOCHS: "3", BS: "16"}
+    deps: [torch, transformers]
+gates:
+  quality: {cer_max: 0.10}
+  parity: {agree_min: 0.98}
+  convention: row-mean
+```
+
+Stages plan to HF Jobs (the planner translates params to the trainer's
+environment); gates are enforced by `src/pipeline/gates.py` — quality,
+parity, license, conformance, regression, graph-io, budgets. A gate
+failure blocks publish; that is the point.
+
+## The eval-set expectation
+
+A held-out split your gate numbers are honest against — never rows the
+model trained on. The regression gate compares against the registry's
+best-known numbers; a worse candidate flags for owner review instead of
+shipping silently.
+
+## What happens on your PR
+
+1. Contracts validation (`tests/test_pipeline_contracts.py` shape).
+2. Gates run against your declared numbers.
+3. Conformance: the model ships frozen fixtures (12+ vectors through
+   the reference decoder) that the ruby/ts/py suites byte-execute.
+4. Publish is owner-gated: explicit version, owner approval.
+
+## A worked example to copy
+
+The smallest complete path in the repo today: `khm-dict` +
+`tha-phonemic-v3` (corpora) with the thai lexicon trainer — see
+`TODO.sota/67-b6-thai-lexicon.md` for the full run log, and
+`docs/naming/` for how models are named (names target the output
+convention).