test(config): add migration tests for litellm provider

* Implement tests for migrating configuration from v1 to v2 for the litellm provider.
* Validate the structure and values of the migrated configuration.
* Ensure migration rejects newer versions of the configuration.
fix(validate): enhance AI provider validation logic
* Consolidate provider validation into a dedicated method.
* Ensure at least one provider is specified and validate its type.
* Check for required fields based on provider type.
fix(mcpserver): update tool set to use new enrichment tool
* Replace RetryMetadataTool with RetryEnrichmentTool in the ToolSet.
fix(tools): refactor tools to use embedding and metadata runners
* Update tools to utilize EmbeddingRunner and MetadataRunner instead of Provider.
* Adjust method calls to align with the new runner interfaces.

changelog.md

@@ -0,0 +1,80 @@
+# Changelog
+
+## 2026-04-21
+
+### 2026-04-21 21h - Config Schema v2 Introduced
+
+- Refactored configuration to schema version `2` with named AI providers and role-based model chains.
+- Added support for per-role primary and fallback targets for embeddings and metadata.
+- Added optional background role overrides for backfill and metadata retry workers.
+
+### 2026-04-21 21h - Automatic v1 -> v2 Migration
+
+- Added config migration framework with explicit schema versioning.
+- Implemented `v1 -> v2` migration to transform legacy provider blocks into named providers + role chains.
+- Loader now auto-migrates older config files, rewrites migrated YAML, and creates timestamped backups.
+
+### 2026-04-21 21h - AI Registry and Role Runners
+
+- Added `ai.Registry` to build provider clients from named provider config entries.
+- Added `EmbeddingRunner` and `MetadataRunner` with sequential fallback execution.
+- Added target health tracking with cooldowns for transient/permanent/empty-response failures.
+
+### 2026-04-21 21h - App and Tool Wiring Updates
+
+- Rewired app startup to use provider registry + role runners for foreground and background flows.
+- Updated capture, search, summarize, context, recall, backfill, metadata retry, and reparse paths to use new runners.
+- Preserved environment override behavior for provider credentials/endpoints across matching provider types.
+
+### 2026-04-21 21h - Migrate Config CLI Added
+
+- Added `cmd/amcs-migrate-config` CLI to migrate config files to the current schema version.
+- Supports dry-run output and in-place write mode with automatic backup file creation.
+
+### 2026-04-21 21h - Tests and Documentation Updated
+
+- Added focused tests for config migration, AI registry behavior, and runner fallback behavior.
+- Updated `configs/config.example.yaml` to the new v2 schema.
+- Updated README configuration sections and migration guidance to reflect v2 and `amcs-migrate-config` usage.
+
+### 2026-04-21 21h - Uncommitted File Change List
+
+- Modified: `.gitignore`
+- Modified: `README.md`
+- Modified: `configs/config.example.yaml`
+- Modified: `internal/ai/compat/client.go`
+- Modified: `internal/ai/compat/client_test.go`
+- Modified: `internal/app/app.go`
+- Modified: `internal/config/config.go`
+- Modified: `internal/config/loader.go`
+- Modified: `internal/config/loader_test.go`
+- Modified: `internal/config/validate.go`
+- Modified: `internal/config/validate_test.go`
+- Modified: `internal/mcpserver/server.go`
+- Modified: `internal/mcpserver/streamable_integration_test.go`
+- Modified: `internal/tools/backfill.go`
+- Modified: `internal/tools/capture.go`
+- Modified: `internal/tools/context.go`
+- Modified: `internal/tools/enrichment_retry.go`
+- Modified: `internal/tools/links.go`
+- Modified: `internal/tools/metadata_retry.go`
+- Modified: `internal/tools/recall.go`
+- Modified: `internal/tools/reparse_metadata.go`
+- Modified: `internal/tools/retrieval.go`
+- Modified: `internal/tools/search.go`
+- Modified: `internal/tools/summarize.go`
+- Modified: `internal/tools/update.go`
+- Deleted: `internal/ai/factory.go`
+- Deleted: `internal/ai/factory_test.go`
+- Deleted: `internal/ai/litellm/client.go`
+- Deleted: `internal/ai/ollama/client.go`
+- Deleted: `internal/ai/openrouter/client.go`
+- Deleted: `internal/ai/provider.go`
+- New: `changelog.md`
+- New: `cmd/amcs-migrate-config/main.go`
+- New: `internal/ai/registry.go`
+- New: `internal/ai/registry_test.go`
+- New: `internal/ai/runner.go`
+- New: `internal/ai/runner_test.go`
+- New: `internal/config/migrate.go`
+- New: `internal/config/migrate_test.go`