Follow-up implementation for #6674.

Proposed Changes

• replace panic paths in loader with proper error returns:
  • missing dialers by execution id
  • nil waitgroup in template loading path
• update function signatures to propagate errors:
  • Store.Load
  • Store.LoadTemplates
  • Store.LoadTemplatesWithTags
• update all affected callers to handle and propagate returned errors:
  • runner, lazy auth path, sdk/multi-sdk, integration test entry, server sdk, automaticscan
• include regression test for missing dialers error path
• include benchmark/test call-site updates for new return signatures
• include nitpick cleanup from review pass:
  • avoid redundant Wrapf(..., "%s", err) wrapping in SDK entry points
  • use require.ErrorContains in loader tests

Proof

# compile-check for touched integration/sdks paths
go test ./lib ./internal/server ./cmd/integration-test -run TestNonExistent -count=1

# behavioral/unit checks for modified runtime paths
go test ./pkg/catalog/loader ./pkg/protocols/common/automaticscan ./internal/runner -count=1

Checklist

• PR created against dev
• Tests/compile checks provided for touched paths
• Regression assertion added for dialer-missing error behavior

/claim #6674

Summary by CodeRabbit

• Bug Fixes

  • Template-loading failures now surface clear, propagated errors; missing or duplicate templates are detected and reported.
  • Missing connectors/dialers now produce explicit errors instead of silent failures.

• Refactor

  • Template-loading APIs and execution paths updated to return and propagate load errors so callers halt or handle failures gracefully.
  • Error messages standardized and simplified for clearer reporting.

• Tests

  • Added a test verifying error reporting when required dialers/connectors are missing.