Bound generated text content and diagnostics

docs/internal/generatedtext.md

@@ -24,6 +24,20 @@ prose to render. Typed decoding requires the exact lowercase JSON field names,
 rejects missing, duplicate, case-variant, and unknown fields, and checks field
 shapes; no general-purpose JSON Schema engine is used at runtime.
 
+The validator accepts at most 64 KiB of raw JSON before it allocates typed
+values. Its JSON Schemas and typed checks limit `summary` and
+`precipitation_timing` to 4,000 characters each. Hourly
+`forecast_discussion` is limited to 12,000 characters. Day-style discussion
+accepts at most 12 paragraphs of at most 4,000 characters each. Across all
+prose fields, one report may contain at most 20,000 characters. These bounds
+apply before trimming, filtering, normalization, and template rendering.
+
+Malformed JSON and field values return short, content-safe errors. They name
+only canonical fields where useful and never echo provider values or unknown
+field names. The Promptkit adapter also drops an oversized provider result
+before copying it into execution or debug state; direct executor implementations
+receive the same enforcement in this package.
+
 ## Render contexts
 
 The catalog's report-specific builders receive briefing metadata, a rich module