feat: synthesise response bodies from OpenAPI schemas

[MaxMichel2]

Summary

Stacked on #131 (PR chain: #123 → #124 → #127 → #128 → #129 → #126 → #131 → this) — merge in order.

The OpenAPI parser had no schema support at all — a status code with a declared content.<mediaType>.schema but no examples showed zero mockable variants. This adds response-body synthesis for exactly that case, deliberately narrow (not full JSON Schema conformance): primitives, enum, object, array, allOf (merged), and oneOf (first variant) — see docs/modules/networkmock-core.md's new "Schema-based response synthesis" section for the exact per-shape rules.

What changed

• SchemaObject/DiscriminatorObject (OpenApiDocument.kt): follow the existing $ref-capable-object style (HeaderObject/ParameterObject). ComponentsObject gains a schemas map; MediaTypeObject gains a schema field.
• SchemaSynthesizer (new file, openapi/SchemaSynthesizer.kt, internal object): synthesize(schema, resolveSchema) recursively resolves $refs via a caller-supplied callback (reusing OpenApiParser's own ref-resolution machinery from fix: resolve dollar-ref chains and disambiguate component sections #131 — a new ParseContext.resolveSchema resolves against components.schemas) and produces one plausible JsonElement per schema shape.
• ResponseContent (new sealed interface, OpenApiParser.kt): generalizes ResolvedResponse's file-path-only content into FromFile/Synthesized, so a synthesized body flows through the same response index as a file-backed one, cached alongside it (no regeneration per discovery pass).
• resolveResponseIndex: per-media-type example resolution extracted into a new resolveMediaTypeResponses helper (keeps the function under detekt's LongMethod threshold) — for each media type, declared examples are resolved first; only if none are declared and a schema is present does synthesis kick in. A status code with any declared examples for a media type never falls back to synthesis for that media type, even if it also declares a schema.
• MockResponse.isSynthesized: Boolean (default false, additive): threaded through MockConfigRepository.loadResponseFromPath. The operation picker page shows a small "Generated" badge (MockItem.kt) on a synthesized response's row, styled after EndpointCard's method badge (Box + RoundedCornerShape(4.dp) + labelSmall).

Scope decisions (per the handoff)

• nullable is read but ignored — a real value is always synthesized, never JSON null; this library mocks responses, it doesn't exercise null-handling.
• oneOf + discriminator: synthesizes the first declared variant regardless of whether a discriminator is present. There's no concrete request/response data at spec-parse time to disambiguate against, so full discriminator-based variant selection isn't attempted — noted here rather than built speculatively.
• allOf conflicts: two members declaring the same property with different schemas throws a clear error rather than silently picking one.
• Composition (allOf/oneOf) didn't turn out messier than expected against the test fixtures tried, so this shipped as scoped rather than being cut down to primitives/object/array only.

Public API

api.txt regenerated for devview-networkmock-core via metalavaGenerateSignature — purely additive (MockResponse gains a defaulted constructor parameter, a component7(), and a getter/property; MockResponse.Companion.create gains a defaulted parameter). docs/modules/networkmock-core.md updated to match (new "Schema-based response synthesis" section; the $ref resolution section already covered the reused ref machinery in #131).

Tests

• SchemaSynthesizerTest.kt (new, 17 tests): each primitive type, enum, nested object (including the no-explicit-type-but-properties case), array (including the no-items error case), allOf merge (including the conflicting-members error case and the same-property-redeclared-identically non-conflict case), oneOf with and without discriminator (both falling back to the first variant), $ref resolution via the callback, and the no-recognizable-shape error case.
• MockConfigRepositoryTest.kt (+3 end-to-end wiring tests): a schema-only status code synthesizes a body with isSynthesized = true; a status code with both examples and a schema prefers the examples (isSynthesized = false); a $ref'd schema under components.schemas resolves correctly before synthesizing.

Verification

.\gradlew.bat detektFull -Pandroidx.baselineprofile.skipgeneration
.\gradlew.bat testAndroidHostTest -Pandroidx.baselineprofile.skipgeneration
.\gradlew.bat :konsist:test -Pandroidx.baselineprofile.skipgeneration
.\gradlew.bat :devview-networkmock:compileAndroidDeviceTest -Pandroidx.baselineprofile.skipgeneration
.\gradlew.bat :sample:androidApp:assembleDebug -Pandroidx.baselineprofile.skipgeneration

All green, including a full repo-wide testAndroidHostTest run to confirm no fallout outside the networkmock modules.

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