Add support for validating config initializing plugin using zod schema

[rithviknishad]

Plugins should be able to optionally specify a configSchema in it's plugin manifest which can be used to validate the configuration. configSchema would be a zod schema passed to the manifest and the plugin runner would be responsible of validating the configuration before calling setup or scrape.

[rbalogic]

@rithviknishad I'm taking this up.

Planned approach for this issue:

• Optional configSchema support: I’m going to add optional configSchema support to plugin manifests and have the plugin runner validate plugin configurations before invoking any lifecycle methods.
• Validation Logic: The runner will validate plugins.<id>.config once after loading the plugin, fail fast with a clear error if validation fails, and pass the parsed result into ctx.config for setup(), scrape(), and aggregate().
• Testing & Documentation: I’m also planning to cover this with runner/loader tests and update the plugin API docs and scaffolding so plugin authors can define configSchema directly in their manifest.

I’ll share a PR once the change is ready.

[rbalogic]

Opened PR for this work: #768

Summary of Changes

• Config Validation: Adds optional configSchema support on plugin manifests.
• Fail-Fast Logic: The plugin runner now validates plugins.<id>.config before any lifecycle methods run. If a plugin defines a schema, the runner fails fast on invalid configurations.
• Context Enrichment: Passes the parsed Zod result into ctx.config for use in setup(), scrape(), and aggregate().
• Quality Assurance:
  • Includes loader/runner test coverage for the new behavior.
  • Updates plugin API docs and scaffolding to assist plugin authors with configSchema implementation.