Show available workflows when workflow not found in add command

[Copilot]

When gh aw add owner/repo/workflow-name fails because the workflow doesn't exist, users get generic help text with no indication of what workflows are actually available in the installed package.

Changes

• New function displayAvailableWorkflows(): Lists all workflows from the installed package with example commands
• Enhanced error path in addWorkflowWithTracking(): Calls displayAvailableWorkflows() when workflow not found, falls back to generic help on failure
• Tests: Coverage for listing workflows, version handling, and edge cases (empty package, missing package)

Example

Before:

✗ Workflow 'workflows/daily-news.md' not found.

To add workflows to your project:
=================================
Use the 'add' command with repository/workflow specifications:
  gh aw add owner/repo/workflow-name

After:

✗ Workflow 'workflows/daily-news.md' not found.

ℹ Available workflows in githubnext/agentics:

  • ci-doctor
  • daily-plan
  • weekly-summary

Example:
  gh aw add githubnext/agentics/ci-doctor

Original prompt

When the add command tries to add a workflow name that does not exist, show the list of potential workflow names to the user. Reuse the code that lists the workflow names.

WRONG

@pelikhan ➜ /workspaces/gh-aw (main) $ ./gh-aw add githubnext/agentics/daily-news
Package githubnext/agentics already exists. Updating...
Successfully installed package: githubnext/agentics
✗ Workflow 'workflows/daily-news.md' not found.

To add workflows to your project:
=================================
Use the 'add' command with repository/workflow specifications:
  gh aw add owner/repo/workflow-name
  gh aw add owner/repo/workflow-name@version

Example:
  gh aw add githubnext/agentics/ci-doctor
  gh aw add githubnext/agentics/daily-plan@main
✗ failed to add workflow 'githubnext/agentics/workflows/daily-news.md': workflow not found: workflows/daily-news.md

BETTER: suggest list of availabe names.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[Copilot]

Pull Request Overview

This PR enhances the add command's error handling by displaying available workflows from an installed package when a specific workflow is not found, providing more helpful guidance to users.

Key Changes:

• Added displayAvailableWorkflows() function that lists workflows from installed packages with examples
• Modified error handling in addWorkflowWithTracking() to call the new function before falling back to generic help
• Added comprehensive test coverage for the new functionality including edge cases (no workflows, package not found, with/without version)

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
pkg/cli/add_workflow_not_found_test.go	New test file with 4 test cases covering workflow listing scenarios: basic display, version handling, empty package, and missing package
pkg/cli/add_command.go	Added displayAvailableWorkflows() function and integrated it into workflow-not-found error flow to provide contextual help instead of generic instructions

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Duplicated workflow name extraction logic: The logic for extracting workflow names from paths (lines 320-326) is duplicated almost identically in lines 344-348 for the example workflow. Consider extracting this into a small helper function to avoid code duplication and make the logic easier to maintain.

[Copilot]

Missing error check: The return value from buf.ReadFrom(r) is not checked. While this is unlikely to fail in tests, it's best practice to check errors, especially since other I/O operations in the same tests do check errors.

Suggested change

	buf.ReadFrom(r)
	if _, err := buf.ReadFrom(r); err != nil {
	t.Fatalf("Failed to read from pipe: %v", err)
	}

[Copilot]

Missing error check: The return value from buf.ReadFrom(r) is not checked. While this is unlikely to fail in tests, it's best practice to check errors, especially since other I/O operations in the same tests do check errors.

Suggested change

	buf.ReadFrom(r)
	if _, err := buf.ReadFrom(r); err != nil {
	t.Fatalf("Failed to read from pipe: %v", err)
	}