[WIP] Wrap errors.New() calls with fmt.Errorf for better context

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[plan] Add error context wrapping to plain errors.New() calls</issue_title>
<issue_description>## Objective

Convert 80 instances of errors.New() to properly wrapped errors using fmt.Errorf with %w to preserve error chains and prevent context loss.

Context

Currently 80 plain errors.New() calls lose valuable error chain context, making debugging difficult. This contrasts with the 809 (55.8%) properly wrapped errors elsewhere in the codebase. Preserving error chains enables better error analysis and debugging.

Files to Modify

Focus on validation files in pkg/workflow/:

• pkg/workflow/mcp-config.go (999 LOC)
• pkg/workflow/safe_outputs_config_generation.go (854 LOC)
• pkg/workflow/validation*.go files (63 validation files total)
• Other pkg/workflow/*.go files with plain errors.New() usage

Approach

Replace plain error creation with wrapped errors:

// OLD - Loses context
return errors.New("validation failed")

// NEW - Preserves context (when underlying error exists)
return fmt.Errorf("validation failed: %w", underlyingErr)

// OR - Add actionable context (when no underlying error)
return fmt.Errorf("validation failed: field '%s' is required but not provided. Add the field to your workflow frontmatter", fieldName)

Key principles:

1. Use %w (not %v) to preserve error chains for errors.Is() and errors.As() checks
2. Add actionable context: what failed, why, what to do
3. Include specific values in error messages (field names, etc.)

Acceptance Criteria

• All errors.New() calls in pkg/workflow/ reviewed
• Context-sensitive errors converted to fmt.Errorf with %w wrapping
• Error messages include actionable context (what/why/how to fix)
• No regression in error handling tests
• Error chains preserve root cause information

Validation

Run after changes:

make test-unit
# Check improvement in wrapping ratio
grep -r "fmt.Errorf.*%w" pkg/workflow/ | wc -l
grep -r "errors.New" pkg/workflow/ | wc -l

Related to #9236

AI generated by Plan Command for discussion #9231

Comments on the Issue (you are @copilot in this section)

• Fixes [plan] Add error context wrapping to plain errors.New() calls #9238

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