Document Tomorrow generated-text workflow

docs/internal/generatedtext.md

@@ -7,21 +7,23 @@ This document describes structured generated-text handling in
 
 `internal/generatedtext` validates structured text returned for
 generated-text-template reports and builds curated render contexts for
-templates. The first implemented contract is the Hourly Report.
+templates. The implemented contracts are Tomorrow Report and Hourly Report.
 
 ## Inputs And Outputs
 
 Inputs:
 
-- raw Hourly Report GeneratedText JSON
+- raw GeneratedText JSON for Tomorrow Report or Hourly Report
 - report metadata from `internal/briefing`
 - a module snapshot from `internal/module`
-- validated hourly generated text
+- validated generated text
 
 Outputs:
 
+- typed `Tomorrow` generated text
 - typed `Hourly` generated text
-- normalized stable JSON for validated hourly generated text
+- normalized stable JSON for validated generated text
+- typed `TomorrowRenderContext` values for `internal/reporttemplate`
 - typed `HourlyRenderContext` values for `internal/reporttemplate`
 
 The hourly generated text JSON accepts:
@@ -39,6 +41,22 @@ The hourly generated text JSON accepts:
 `precipitation_timing` and `confidence` are optional and omitted from normalized
 JSON when blank.
 
+The Tomorrow generated text JSON accepts:
+
+```json
+{
+  "summary": "string",
+  "forecast_discussion": ["string"],
+  "precipitation_timing": "string",
+  "confidence": "string"
+}
+```
+
+`summary` is required after trimming whitespace. `forecast_discussion` must
+contain at least one nonblank paragraph after trimming blank items.
+`precipitation_timing` and `confidence` are optional and omitted from normalized
+JSON when blank.
+
 ## Boundaries
 
 - This package owns typed generated-text validation and render-context shaping.
@@ -54,7 +72,8 @@ JSON when blank.
 
 - Malformed generated-text JSON fails with decode context.
 - Unknown generated-text JSON fields fail during decoding.
-- Empty required hourly fields fail after trimming whitespace.
+- Empty required fields fail after trimming whitespace.
+- Tomorrow forecast discussion fails when no nonblank paragraphs remain.
 - Missing optional render-context stanzas become nil module pointers.
 - Invalid render metadata, including missing timezone, missing generated time,
   or invalid valid period, fails before template rendering.
@@ -64,6 +83,7 @@ JSON when blank.
 Inspect:
 
 - `internal/generatedtext/hourly_test.go`
+- `internal/generatedtext/tomorrow_test.go`
 - `internal/generatedtext/render_context_test.go`
 
 ## Invariants