Apply PR #36 review-thread fixes for config path, ClickHouse docs, and test cleanup

[Copilot]

This addresses the review-thread comments on PR #36 by fixing the default config-file resolution in cmd/server, correcting ClickHouse schema-management documentation, and tightening a shared-state test. It also aligns the RenderTemplate docstring with the actual missing-key behavior.

• Startup config path

  • Use the existing config-path resolver for the normal app.Run(...) path.
  • Fall back to plain yagpcc.yaml when --config-path is unset, instead of constructing /yagpcc.yaml.
  • Add a focused test covering both the cwd fallback and explicit config directory behavior.

  func runtimeConfigFilePath() string {
  	if path := configFilePath(); path != "" {
  		return path
  	}
  	return configFile
  }

• ClickHouse schema docs

  • Replace the non-existent --dump-only reference with the implemented CLI/config contract:
    • CLI: --dump-schema
    • Config: schema_management: dump_only
  • Correct the dump_only lifecycle description to match actual behavior: the process exits after printing DDL; it does not continue starting the master.

• Template API comment accuracy

  • Update RenderTemplate comments to state that missing keys fail with an error, matching template.Option("missingkey=error").

• Test isolation

  • Restore internal/storage.CurrentTime with t.Cleanup(...) in aggregated_storage_test.go so the package-global override cannot leak into later tests.