Add module contracts and registry validation

docs/internal/briefing.md

@@ -21,6 +21,8 @@ Outputs:
 
 - `briefing.Package` with common metadata and one report-specific content
   object for Daily, 3-Day, Weekend, or Storm Report
+- module registry definitions for known module IDs, stanza names, option
+  shapes, fact requirements, report compatibility, and missing-data behavior
 - optional `currentConditions` prompt context from normalized
   `/conditions/current` data when available
 - optional structured `weatherStory` context on report-specific briefing
@@ -30,6 +32,8 @@ Outputs:
 ## Boundaries
 
 - This package selects and shapes weather facts for prompts.
+- It owns module registry validation, but app orchestration does not execute
+  modules yet.
 - It does not fetch weather data, compare prior snapshots, build
   `data_package` files, invoke Scriptorium, or write workflow metadata.
 
@@ -65,6 +69,10 @@ None. Builders either return a complete briefing package or an error.
   least one derived summary.
 - Storm briefing construction requires a Storm Report definition and forecast
   bundle.
+- Module registry construction rejects duplicate module IDs and duplicate
+  stanza names.
+- Module composition validation rejects unknown modules, duplicate modules,
+  incompatible report/module combinations, and invalid typed options.
 - Save failures include path and operation context.
 
 ## Tests
@@ -75,6 +83,7 @@ Inspect:
 - `internal/briefing/three_day_test.go`
 - `internal/briefing/weekend_test.go`
 - `internal/briefing/storm_test.go`
+- `internal/briefing/modules_test.go`
 - `internal/app/app_test.go`
 
 ## Invariants

docs/internal/module.md

@@ -0,0 +1,58 @@
+# Module Contract Internals
+
+This document describes the implemented module contract boundary.
+
+## Purpose
+
+`internal/module` defines stable module IDs, typed configuration items, module
+outputs, and module snapshots. It is a shared contract imported by report
+definitions and briefing registry code.
+
+## Inputs And Outputs
+
+Inputs:
+
+- ordered `module.ConfigItem` values from report definitions
+- `module.Output` values assembled by callers
+
+Outputs:
+
+- stable `module.ID` constants
+- typed option structs for known modules
+- `module.Snapshot` with ordered outputs and schema version
+- typed stanza lookup through `module.StanzaValue`
+
+## Boundaries
+
+- This package owns shared module identifiers and output envelope contracts.
+- It does not define report IDs, build briefing stanzas, fetch weather data,
+  derive facts, write state, or invoke Scriptorium.
+
+## State Or Manifest Behavior
+
+`module.Snapshot` uses schema version `weatherreporter.modules.v1`. Snapshot
+validation rejects duplicate module outputs and duplicate stanza names while
+preserving output order.
+
+## Failure Behavior
+
+- Snapshot validation fails when schema version, module ID, or stanza name is
+  missing.
+- Snapshot validation fails on duplicate module IDs or duplicate stanza names.
+- Typed stanza lookup returns `found=false` for missing stanzas and wraps JSON
+  marshal/decode failures with stanza context.
+
+## Tests
+
+Inspect:
+
+- `internal/module/module_test.go`
+- `internal/briefing/modules_test.go`
+- `internal/report/period_test.go`
+
+## Invariants
+
+- `internal/module` does not import `internal/report`.
+- Module IDs are stable strings.
+- Each module output has exactly one stanza name and one typed value.
+- Snapshot output order is caller-owned and preserved.

docs/internal/report-registry.md

@@ -23,6 +23,7 @@ Each report definition declares:
 - generated-report eligibility
 - prior-report compatibility list
 - morning or evening batch membership
+- default ordered module composition
 
 ## Implemented Reports
 
@@ -70,6 +71,7 @@ output path copying uses batch output names from report definitions.
 - State paths use `ArtifactGroup`.
 - Batch output copies use `BatchOutputName`.
 - Generation checks `Generated`.
+- Module composition defaults use `Modules`.
 - Prior lookup checks `CompatiblePriorIDs` and the comparison strategy.
 - RunIDs include the resolved report ID.
 
@@ -93,5 +95,5 @@ Inspect:
 - Daily Today and Daily Tomorrow both use `weather.daily_report`.
 - Valid periods are half-open intervals independent of rendered report text.
 - Artifact grouping, batch output filenames, generated-report eligibility,
-  comparison compatibility, and comparison strategy are declared by report
-  definition.
+  default module composition, comparison compatibility, and comparison strategy
+  are declared by report definition.

docs/policy/development.md

@@ -20,6 +20,7 @@ Developers and LLM coding agents should use it with
   source warnings.
 - `internal/forecast`: deterministic forecast derivation.
 - `internal/facts`: collected and derived report fact contracts.
+- `internal/module`: module IDs, config items, output envelopes, and snapshots.
 - `internal/report`: report definitions, valid periods, batches, output names,
   and comparison declarations.
 - `internal/briefing`: report-specific briefing package builders.