fix: allow converting string literal block with list

[Yuan325]

This PR updates the following:

• Fix YAML String Block Conversion: Resolved an issue where multiline strings (like tool descriptions) containing list syntax were being re-encoded as double-quoted strings with explicit \n characters. They now correctly use the | literal block style as expected.

description: |
  this is the description
  this tool uses the following parameter:
  - param_1
  - param_2

# will turn into 

description: "this is the description\nthis tool uses the following parameter:\n-param_1\n-param_2"

• Updated the converter to identify and retain initial comment lines/license headers at the top of configuration files.
• Updated migration completion status to reflect "ended" state.
• Update to use "v1" -> "nested format" and "v2" -> "flat format"
• Remove "authSources" when checking for keys. We had previously removed support for "authSources".

Fixes #3023

[gemini-code-assist]

Code Review

This pull request updates the configuration conversion logic to preserve top-level comments and empty lines, while transitioning terminology from 'v1/v2' to 'nested/flat' formats. It also enables literal style for multiline strings in YAML encoding. Review feedback suggests renaming variables for consistency, adding the missing 'authSources' key to the migration list, correcting comment numbering, and updating related informational logs that have become inaccurate due to these changes.

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cmd/internal/config.go (147)

To align with the PR's goal of moving away from "v1/v2" terminology, this variable should be renamed (e.g., to nestedFormatKeys). Additionally, authSources is missing from this list, which prevents the migration tool from detecting and converting documents that use the deprecated authSources key, even though it is explicitly handled in the switch statement at line 170.

	nestedFormatKeys := []string{"sources", "authSources", "authServices", "embeddingModels", "tools", "toolsets", "prompts"}

cmd/internal/config.go (126)

The comment starts with "2.", but there is no preceding "1." step in this function. It is better to use a descriptive comment without numbering to avoid confusion.

	// Manually copy top-level comments and empty lines from the source

cmd/internal/config.go (163)

Update the variable name to match the suggested rename at line 147.

			if slices.Contains(nestedFormatKeys, key) {

cmd/internal/migrate/command.go (130)

While updating this message, please note that the informational log at line 68 ("any comments... will not be preserved") is now incorrect because of the changes in ConvertConfig that preserve top-level comments. Since line 68 is outside the current diff hunks, it should be updated in a separate commit or by expanding the PR scope to ensure users are not given misleading information.