Add 3-Day Outlook generation

docs/internal/briefing.md

@@ -6,7 +6,7 @@ This document describes the implemented briefing package boundary.
 
 `internal/briefing` builds structured report-specific briefing packages from
 forecast summaries and report metadata. The package currently implements Daily
-Today and Daily Tomorrow briefing content.
+Today, Daily Tomorrow, and 3-Day Outlook briefing content.
 
 ## Inputs and Outputs
 
@@ -14,12 +14,13 @@ Inputs:
 
 - resolved report definition and valid period
 - forecast bundle
-- derived daily forecast summary
+- derived forecast summary or summaries
 - configured units and timezone
 
 Output:
 
-- `briefing.Package` JSON containing common metadata and Daily briefing content
+- `briefing.Package` JSON containing common metadata and report-specific
+  briefing content
 
 ## Boundaries
 
@@ -37,12 +38,18 @@ Output:
   story context when available.
 - Daily Tomorrow also includes planning inputs for morning readiness,
   commute/school/workday concerns, and what may change overnight.
+- 3-Day content includes one summary per local day or partial day, with overall
+  character, temperature range, precipitation, wind, risk, outdoor-window, and
+  alert inputs, plus broader discussion and weather-story context when
+  available.
 - Briefing JSON is written atomically by `briefing.Save`.
 
 ## Failure Behavior
 
 - Daily briefing construction requires a Daily report definition and a derived
   daily forecast summary.
+- 3-Day briefing construction requires a 3-Day report definition and at least
+  one derived daily summary in the outlook period.
 - Save failures include path and operation context.
 
 ## Tests
@@ -50,6 +57,7 @@ Output:
 Inspect:
 
 - `internal/briefing/daily_test.go`
+- `internal/briefing/three_day_test.go`
 - `internal/app/app_test.go`
 - `internal/cli/root_test.go`
 

docs/internal/changes.md

@@ -11,8 +11,8 @@ produces compact change records for prompt input data packages.
 
 Inputs:
 
-- prior Daily briefing package
-- current Daily briefing package
+- prior briefing package
+- current briefing package
 - configured Recent Changes thresholds
 
 Output:
@@ -37,7 +37,7 @@ The app maps these config fields into comparison thresholds:
 
 ## Behavior
 
-Daily comparison currently detects:
+Daily and 3-Day comparison currently detect:
 
 - temperature changes crossing configured thresholds
 - precipitation probability and timing changes
@@ -47,17 +47,20 @@ Daily comparison currently detects:
 
 When no prior comparable snapshot exists, the app sends an empty Recent Changes
 section in the data package. Daily Today and Daily Tomorrow are compatible for
-same-valid-date comparison through the report registry.
+same-valid-date comparison through the report registry. 3-Day Outlook compares
+with prior 3-Day Outlook snapshots for the same valid local date.
 
 ## Failure Behavior
 
-Daily comparison requires both inputs to contain Daily briefing content.
+Daily comparison requires both inputs to contain Daily briefing content. 3-Day
+comparison requires both inputs to contain 3-Day briefing content.
 
 ## Tests
 
 Inspect:
 
 - `internal/changes/daily_test.go`
+- `internal/changes/three_day_test.go`
 - `internal/app/app_test.go`
 
 ## Invariants

docs/internal/forecast-derivation.md

@@ -6,8 +6,8 @@ boundary.
 ## Purpose
 
 `internal/forecast` converts a normalized forecast bundle into inspectable
-daily daypart summaries. These summaries are structured data for later briefing
-builders; they are not rendered report text.
+daily and multi-day daypart summaries. These summaries are structured data for
+later briefing builders; they are not rendered report text.
 
 ## Inputs and Outputs
 
@@ -15,6 +15,7 @@ Inputs:
 
 - `forecast.Bundle`
 - local date and timezone
+- report period, for multi-day summaries
 - configured daypart definitions with `HH:MM` start and end values
 
 Output:
@@ -22,6 +23,8 @@ Output:
 - `forecast.DailySummary` with a civil-day period, daypart summaries, selected
   narrative periods, alert overlaps, discussion context, source warnings, and
   source provenance.
+- `forecast.BuildPeriodDailySummaries` output with one clipped daily summary
+  for each local day or partial day in a report period.
 
 ## Boundaries
 
@@ -41,6 +44,8 @@ Output:
 - Alerts are selected by overlap with the daily period and each daypart.
 - Narrative periods and discussion context are selected as broader source
   context for later briefing builders.
+- Multi-day period summaries clip the first and last local days to the resolved
+  report period before selecting hourly periods and alerts.
 
 ## Failure Behavior
 

docs/internal/prompt-input.md

@@ -11,7 +11,7 @@ This document describes the implemented prompt input package boundary.
 
 Input:
 
-- `briefing.Package`
+- `briefing.Package` containing Daily-family or 3-Day Outlook content
 
 Output:
 

docs/internal/state.md

@@ -5,7 +5,7 @@ This document describes the implemented filesystem state boundary.
 ## Purpose
 
 `internal/state` owns durable artifact paths, atomic JSON writes, metadata, and
-prior Daily snapshot lookup.
+prior comparable snapshot lookup.
 
 ## Inputs and Outputs
 
@@ -25,8 +25,8 @@ Outputs:
 - render preflight JSON
 - Markdown report path
 - metadata JSON
-- prior Daily snapshot metadata when available
-- prior Daily briefing package when loaded by path
+- prior comparable snapshot metadata when available
+- prior briefing package when loaded by path
 
 ## Boundaries
 
@@ -48,12 +48,13 @@ Workspace subdirectories must be relative paths that stay under
 ## State Behavior
 
 Managed artifact names use RunID, which is generated from report generation time
-and report ID. Daily metadata is stored beside Daily briefing snapshots by valid
-local date. Prior Daily snapshot lookup reads metadata for the same valid local
-date and returns the latest earlier compatible Daily Today or Daily Tomorrow
-run. The store can load a briefing snapshot by path for structured comparison.
-The store prepares the managed Markdown report path before `scriptorium run`
-writes it.
+and report ID. Metadata is stored beside briefing snapshots by report group and
+valid local date. Prior snapshot lookup reads metadata for the same valid local
+date and returns the latest earlier compatible run. Daily Today and Daily
+Tomorrow are compatible with each other; 3-Day Outlook is compatible with prior
+3-Day Outlook snapshots. The store can load a briefing snapshot by path for
+structured comparison. The store prepares the managed Markdown report path
+before `scriptorium run` writes it.
 
 ## Failure Behavior