refactor: deprecate is_markdown_buffer and remove dead-code callers

[YousefHadder]

Summary

Deprecate utils.is_markdown_buffer() (which always returns true) with a vim.deprecate() warning targeting removal in 2.0.0. Filetype filtering is handled by the autocmd pattern in init.lua, making this check redundant.

The function is preserved with a deprecation notice so any external callers get a clear warning instead of a hard break.

Changes

• Add vim.deprecate() call to is_markdown_buffer() in utils.lua
• Remove dead-code guard blocks from 8 module enable() functions: callouts, format, footnotes, list, links, images, quote, headers
• Remove unused utils imports from 4 modules that only used it for this function
• Remove corresponding tests from utils_spec.lua (the function is deprecated, not tested)

[Copilot]

Pull request overview

Removes the deprecated utils.is_markdown_buffer() helper (which always returned true) and simplifies feature module enable() implementations by dropping redundant guards, relying on init.lua’s FileType autocmd filtering instead.

Changes:

• Removed is_markdown_buffer() from lua/markdown-plus/utils.lua and deleted its specs.
• Removed now-dead if not utils.is_markdown_buffer() then return end guards from multiple module enable() functions.
• Cleaned up unused utils imports in modules that only used it for the removed helper.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
spec/markdown-plus/utils_spec.lua	Removes tests for the deleted is_markdown_buffer() utility.
lua/markdown-plus/utils.lua	Deletes the deprecated is_markdown_buffer() export.
lua/markdown-plus/callouts/init.lua	Removes redundant markdown-buffer guard in enable().
lua/markdown-plus/quote/init.lua	Removes redundant markdown-buffer guard in enable().
lua/markdown-plus/list/init.lua	Removes redundant guard and drops unused utils require.
lua/markdown-plus/links/init.lua	Removes redundant markdown-buffer guard in enable().
lua/markdown-plus/images/init.lua	Removes redundant markdown-buffer guard in enable().
lua/markdown-plus/headers/init.lua	Removes redundant guard and drops unused utils require.
lua/markdown-plus/format/init.lua	Removes redundant guard and drops unused utils require.
lua/markdown-plus/footnotes/init.lua	Removes redundant guard and drops unused utils require.

[Copilot]

Removing utils.is_markdown_buffer() is a breaking change for any external code that still calls it via require('markdown-plus.utils'), even if it was previously marked deprecated. Consider keeping a temporary compatibility shim (returning true and emitting a deprecation warning) until the next major release.

Suggested change

	---@param str? string String to match
	---@param str string|nil String to match