Add ConfigKit typed configuration loading core

docs/internal/overview.md

@@ -17,6 +17,7 @@ contributor workflow and validation.
 | `examples/go-library/observe` | Demonstrates offline built-in HTTP retry and synchronous metadata observation across structured proposal and assessment runs using embedded sources, two profiles on one finite backend, and an application decision. It is not a public library package. | [Example program](../../examples/go-library/observe/main.go) |
 | `internal/backend` | Constructs each engine's immutable registry from maintained definitions and consumer additions, validates and defensively copies definitions through the shared JSON-value package, and consumes the LLM-owned OpenAI-compatible reserved request-field rule. | [Backend registry](../../internal/backend/registry.go) |
 | `internal/catalog` | Strictly validates imported immutable maintained backend and profile catalog assets before engine assembly uses them. | [Catalog adapter](../../internal/catalog/catalog.go), [internal sources](sources.md#profiles-and-built-ins) |
+| `internal/configuration` | Loads keyed backend, profile, and prompt configuration through ConfigKit, recording effective field presence and validating final backend/profile values. It is not yet connected to engine assembly. | [Typed loader](../../internal/configuration/load.go), [internal sources](sources.md#typed-configuration-loading) |
 | `internal/capacity` | Owns engine-local bounded execution admission and FIFO model-generation permits for limited backend IDs, including cancellation-safe waiter removal and client wrapping. | [Internal capacity management](capacity.md) |
 | `internal/domain` | Defines internal framework values for requests, artifacts, prompt definitions, profiles, execution targets, rendering, generation, and validation, and owns source-neutral invariants for shared execution settings, OpenAI-compatible base endpoints, session identifiers, and output contracts. Source parsing, required fields, other source-specific normalization, defaulting, and boundary-specific error classification remain with their callers. | [Domain declarations](../../internal/domain/domain.go), [endpoint invariant](../../internal/domain/endpoint.go) |
 | `internal/engine` | Assembles external catalogs, Promptkit-owned profiles, repositories, registry, capacity, collaborators, repairer, and the one use-case runner for each engine instance. | [Engine assembly](../../internal/engine/engine.go), [internal sources](sources.md#profiles-and-built-ins), [internal runner](runner.md) |

docs/internal/sources.md

@@ -10,6 +10,19 @@ and the internal engine assembles them behind the public facade's source options
 The [framework format reference](../formats.md) owns the exact file fields,
 validation modes, built-in catalog, and source precedence.
 
+## Typed Configuration Loading
+
+`internal/configuration` now contains a private ConfigKit adapter for keyed
+backend, profile, and prompt mappings. It performs one layered load, records
+effective field presence (including explicit null), normalizes backend and
+profile fields through ConfigKit resolution, and validates final backend and
+profile domain values. A lower-layer domain value replaced before the handoff
+is not separately validated. Its focused tests exercise real ConfigKit loading.
+
+This loader is not yet wired into engine assembly. The public engine continues
+to use the source and repository behavior described below; prompt resource
+capture and full prompt validation are subsequent implementation work.
+
 ## Prompt Definitions
 
 `internal/promptdef` uses one source-neutral flow for prompt selection and

docs/oss/attribution.md

@@ -16,6 +16,20 @@ License and notices: [CC BY-SA 4.0](licenses/CC-BY-SA-4.0.txt) |
 
 [Source](https://gitea.maximumdirect.net/eric/policy/src/commit/d84a38ebab26f048cafbe59a2246700c35d29843).
 
+## ConfigKit
+
+Selected module: `gitea.maximumdirect.net/eric/ConfigKit` at `v0.5.0`.
+
+Copyright (C) 2026 Eric Rakestraw
+
+SPDX-License-Identifier: LGPL-3.0-or-later
+
+License and notices: [LGPL 3.0](../../LICENSE) |
+[COPYRIGHT](https://gitea.maximumdirect.net/eric/ConfigKit/src/commit/dc09959cca4e105f49ec316c6d4ba585bd2340bd/COPYRIGHT) |
+[LICENSE](https://gitea.maximumdirect.net/eric/ConfigKit/src/commit/dc09959cca4e105f49ec316c6d4ba585bd2340bd/LICENSE).
+
+[Source](https://gitea.maximumdirect.net/eric/ConfigKit/src/commit/dc09959cca4e105f49ec316c6d4ba585bd2340bd).
+
 ## Promptkit OpenRouter Catalog
 
 Selected module: `gitea.maximumdirect.net/eric/promptkit-backend-openrouter/v2`
@@ -91,3 +105,22 @@ License and notices: [MIT](licenses/MIT.txt) |
 [NOTICE](https://github.com/go-yaml/yaml/blob/f6f7691b1fdeb513f56608cd2c32c51f8194bf51/NOTICE).
 
 [Source](https://github.com/go-yaml/yaml/tree/f6f7691b1fdeb513f56608cd2c32c51f8194bf51).
+
+## Go YAML v4
+
+Selected module: `go.yaml.in/yaml/v4` at `v4.0.0-rc.6` (transitive dependency).
+
+Copyright 2006-2010 Kirill Simonov
+
+Copyright 2011-2019 Canonical Ltd
+
+Copyright 2025 The go-yaml Project Contributors
+
+SPDX-License-Identifier: MIT AND Apache-2.0
+
+License and notices: [MIT](licenses/MIT.txt) |
+[Apache 2.0](licenses/Apache-2.0.txt) |
+[LICENSE](https://github.com/yaml/go-yaml/blob/1c17b9cee72bf81ae73a8be50fbd7dd3a9985125/LICENSE) |
+[NOTICE](https://github.com/yaml/go-yaml/blob/1c17b9cee72bf81ae73a8be50fbd7dd3a9985125/NOTICE).
+
+[Source](https://github.com/yaml/go-yaml/tree/1c17b9cee72bf81ae73a8be50fbd7dd3a9985125).

docs/roadmap/implementation.md

@@ -305,6 +305,8 @@ and cancellation remain at their established runtime boundaries.
 
 ## Stage 1 — Add The Dependency And Typed Loading Core
 
+**Completed:** 2026-09-30.
+
 Scope: module metadata, `internal/configuration` DTOs, real ConfigKit loading,
 and its focused tests. Leave engine assembly on the old path for this stage.