Add Today generated text assets

docs/internal/generatedtext.md

@@ -9,22 +9,26 @@ This document describes structured generated-text handling in
 generated-text-template reports and builds curated render contexts for
 templates. It also owns the generated-text catalog that connects report
 definitions to validators, render-context builders, schema assets, and template
-assets. The implemented contracts are Tomorrow Report and Hourly Report.
+assets. The implemented contracts are Today, Tomorrow Report, and Hourly
+Report. Today support is internal until a report definition references the
+`today` schema and template IDs.
 
 ## Inputs And Outputs
 
 Inputs:
 
-- raw GeneratedText JSON for Tomorrow Report or Hourly Report
+- raw GeneratedText JSON for Today, Tomorrow Report, or Hourly Report
 - report metadata from `internal/briefing`
 - a module snapshot from `internal/module`
 - validated generated text
 
 Outputs:
 
+- typed `Today` generated text
 - typed `Tomorrow` generated text
 - typed `Hourly` generated text
 - normalized stable JSON for validated generated text
+- typed `TodayRenderContext` values for `internal/reporttemplate`
 - typed `TomorrowRenderContext` values for `internal/reporttemplate`
 - typed `HourlyRenderContext` values for `internal/reporttemplate`
 - generated-text catalog handlers for report definitions that use
@@ -45,6 +49,18 @@ The hourly generated text JSON accepts:
 `precipitation_timing` and `confidence` are optional and omitted from normalized
 JSON when blank.
 
+The Today generated text JSON accepts the same public fields and validation
+rules as Tomorrow:
+
+```json
+{
+  "summary": "string",
+  "forecast_discussion": ["string"],
+  "precipitation_timing": "string",
+  "confidence": "string"
+}
+```
+
 The Tomorrow generated text JSON accepts:
 
 ```json
@@ -79,7 +95,8 @@ JSON when blank.
 - Malformed generated-text JSON fails with decode context.
 - Unknown generated-text JSON fields fail during decoding.
 - Empty required fields fail after trimming whitespace.
-- Tomorrow forecast discussion fails when no nonblank paragraphs remain.
+- Today and 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.
@@ -91,6 +108,7 @@ JSON when blank.
 Inspect:
 
 - `internal/generatedtext/hourly_test.go`
+- `internal/generatedtext/today_test.go`
 - `internal/generatedtext/tomorrow_test.go`
 - `internal/generatedtext/catalog_test.go`
 - `internal/generatedtext/render_context_test.go`