Add config.provider module for centralized application configuration

[Copilot]

• Create module/config_provider.go — ConfigRegistry + ConfigProviderModule + schema/source/expansion utilities
• Create module/config_provider_test.go — unit tests including single-quote regex and sorted missing-keys tests
• Create plugins/configprovider/plugin.go — Plugin with ConfigTransformHook
• Create plugins/configprovider/plugin_test.go — plugin integration tests
• Update plugins/all/all.go, schema/schema.go, schema/module_schema.go, cmd/wfctl/type_registry.go, module/pipeline_template.go
• Fix regex to support both single and double quotes for {{config 'key'}} / {{config "key"}}
• Fix ValidateRequired to sort missing keys for deterministic error messages
• Fix Init doc comment (was incorrectly labelled "Configure")
• Fix misleading file-level package comment

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[Copilot]

Pull request overview

This PR introduces a config.provider module type that acts as a centralized configuration registry for workflow engine applications. It addresses the lack of schema declaration, startup validation, defaults, source layering, and sensitive-value distinction in the existing ${ENV_VAR} expansion mechanism. The config.provider module exposes a {{config "key"}} template function for referencing values across any YAML section (modules, workflows, triggers, pipelines, platform), and operates independently of (and alongside) the existing ${ENV_VAR} expansion.

Changes:

• Adds module/config_provider.go: thread-safe ConfigRegistry, ParseSchema, LoadConfigSources, ValidateRequired, ExpandConfigRefsMap, and the ConfigProviderModule struct
• Adds plugins/configprovider/plugin.go and its tests: a ConfigTransformHook at priority 1000 that resolves {{config "key"}} references before module construction
• Registers config.provider across schema, type registry, and the default plugin set

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
module/config_provider.go	Core implementation: registry, schema parsing, source loading, validation, expansion
module/config_provider_test.go	Comprehensive unit tests for all core functions
plugins/configprovider/plugin.go	Plugin wiring: module factory + ConfigTransformHook
plugins/configprovider/plugin_test.go	Tests for plugin metadata, hook behaviour, expansion
module/pipeline_template.go	Adds config function to template func map for runtime use
schema/schema.go	Adds "config.provider" to coreModuleTypes
schema/module_schema.go	Registers config.provider schema with field definitions
plugins/all/all.go	Adds configprovider plugin to the default plugin set
cmd/wfctl/type_registry.go	Registers config.provider in the wfctl type registry

[intel352]

@copilot apply changes based on the comments in this thread