fix: format wrapped error chains with newlines and indentation

[Copilot]

Long fmt.Errorf-wrapped error chains are rendered as a single hard-to-read line. Each layer of context is colon-concatenated, making it difficult to identify the root cause at a glance.

Changes

• pkg/console/console.go — adds FormatErrorChain(err error) string that walks errors.Unwrap to extract per-level messages and formats them with consistent 2-space indentation. Also handles errors.Join-style multi-errors whose .Error() output contains newlines.
• cmd/gh-aw/main.go — top-level error handler now calls FormatErrorChain(err) instead of FormatErrorMessage(errMsg) for unformatted errors.
• pkg/cli/add_command.go — compile-step error display uses FormatErrorChain.

Before / After

Before:

✗ workflow 'githubnext/agentics/workflows/q.md@main' not found: failed to download workflow from githubnext/agentics/workflows/q.md@main: failed to fetch file content from githubnext/agentics/workflows/q.md@main: HTTP 404: Not Found (https://...)

After:

✗ workflow 'githubnext/agentics/workflows/q.md@main' not found
  failed to download workflow from githubnext/agentics/workflows/q.md@main
  failed to fetch file content from githubnext/agentics/workflows/q.md@main
  HTTP 404: Not Found (https://...)

The suffix-stripping logic assumes the standard fmt.Errorf("prefix: %w", inner) pattern; if the pattern doesn't match the full message is used as a fallback so no information is lost.

[Copilot]

Pull request overview

Improves readability of long fmt.Errorf("%w")-wrapped error chains by rendering each unwrap layer on its own indented line (and indenting joined/multiline errors), then updates CLI call sites to use the new formatting.

Changes:

• Add console.FormatErrorChain(err) plus helpers to unwrap and pretty-print error chains with indentation.
• Switch top-level CLI error printing (and workflow compile error output) to use FormatErrorChain.
• Add unit tests for basic wrapped and joined error formatting behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
pkg/console/console.go	Adds FormatErrorChain and helpers for unwrapping/formatting multiline error chains.
pkg/console/console_formatting_test.go	Adds tests validating basic chain formatting, multiline output, and indentation behavior.
pkg/cli/add_command.go	Uses FormatErrorChain when printing compile errors.
cmd/gh-aw/main.go	Uses FormatErrorChain(err) for unformatted top-level errors.

Comments suppressed due to low confidence (1)

pkg/console/console.go:324

• formatMultilineError currently drops empty continuation lines (if line != ""), which changes the original error text for messages that intentionally include blank lines (e.g. \n\n separators in user instructions). To avoid losing formatting, preserve empty lines by still writing the newline + indentation even when line is empty.

	for _, line := range lines[1:] {
		if line != "" {
			sb.WriteString("\n  ")
			sb.WriteString(line)
		}

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