Document Promptkit report generation

docs/integrations/promptkit.md

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+# Promptkit Integration
+
+Weatherreporter uses Promptkit for all generated-text reports. The four logical prompts are
+`weather.daily_generated_text`, `weather.today_generated_text`,
+`weather.tomorrow_generated_text`, and `weather.hourly_generated_text`, each at version
+`1.0.0`. Their prompt assets and generated-text JSON Schemas are embedded by
+`internal/promptassets`.
+
+Before collection, Weatherreporter inspects the exact prompt version, requires one required
+`data_package` input with content type `application/yaml`, and requires the report's JSON
+Schema output contract. It selects `promptkit.profile` when configured, otherwise the
+prompt's declared default profile. Profiles that require a direct API key are unsupported; a
+profile that reports `APIKeyEnv` requires a nonblank value in that environment variable.
+
+Execution receives the already-persisted YAML package, prepares it once, and returns structured
+JSON that Weatherreporter validates before rendering its own Markdown template. Preparation and
+execution receipts are project-owned, safe provenance records. Content-rich diagnostics are
+opt-in through `--llm-debug-dir`; see [operations](../operations.md) for retention and permissions.
+
+Prompt/profile configuration is owned by the [configuration reference](../config.md). Adapter
+construction and mapping are documented in the [Promptkit adapter internals](../internal/promptkit-adapter.md).
+Durable metadata compatibility is described in [state internals](../internal/state.md).