fix(translator): treat contentSchema and unevaluatedItems as schema slots - #13110

The bug

stripInvalidSchemaConstructs() replaces a truncation placeholder with the permissive {} in every position where a subschema belongs. Forwarding the string instead is invalid JSON Schema, and that 400 is the thing this sanitizer exists to prevent.

SCHEMA_SLOT_KEYS listed ten of the draft 2020-12 applicators and missed two. Measured on release/v3.8.51, feeding { type: "object", [key]: "[MaxDepth]" } through the walker one keyword at a time:

Those two fall through to the scalar branch at the bottom of the walker — the one that deliberately leaves annotation keywords (description, title, pattern, format) as strings — and are forwarded untouched.

The placeholders are real: logTruncation.ts emits [MaxDepth], [Truncated], [Circular], [Object] and [Array] once a schema is deeper than the log depth limit, and SCHEMA_PLACEHOLDER_PATTERN here matches all five.

The repository already disagrees with itself

The opencode plugin's own walker lists both:

// @omniroute/opencode-plugin-v2/src/shared/gemini.ts
/** Keys whose value is itself a schema. */
const SCHEMA_VALUE_KEYS = [
  "items", "additionalItems", "contains", "not", "if", "then", "else",
  "propertyNames", "contentSchema", "unevaluatedItems", "unevaluatedProperties",
];

Two lists of the same thing, kept in step by hand. They agreed on ten entries and diverged on two, and nothing failed when they did — both files compile, both walkers answer, they just answer differently.

The change

Two entries. Nothing else about those keywords changes: an object or array in either position was already recursed into by the fallback branch, a boolean is still preserved rather than widened to {} (contentSchema: false is restrictive and must stay so), and a string that is not a placeholder is still forwarded untouched.

Tests

tests/unit/translator/schema-slot-keys-drift.test.ts, 17 tests. Rather than testing the two new keywords alone, it drives all twelve slots through all five placeholder shapes, so the next keyword to go missing fails here too. It also pins the three properties that keep the fix from being a widening: booleans preserved, non-placeholder strings untouched, and a property named contentSchema still treated as a property.

The second mutation matters: it shows the coverage test is not an all-or-nothing check.

tests/unit/translator/schema-coercion.test.ts, bailian-schema-validation, agentSkills-schemas — 32 passed. eslint --suppressions-location config/quality/eslint-suppressions.json clean.

Independent of #13101 and #13104; different files.