fix: more misc. bug fixes

[dlyongemallo]

• Fix get_style() returning only the first matching style attribute instead of all of them (e.g. "bold" instead of "bold,strikethrough").
• Fix inverted guard conditions in FilePanel and FileHistoryPanel get_item_at_cursor/get_dir_at_cursor that could crash when the panel buffer wasn't loaded.
• Fix unconditional break in deprecated config warning loop that prevented "multi_file" from ever being checked.
• Fix HgAdapter.parse_revs error check that silently skipped failures when exec_sync returned nil.
• Fix typo: merge_layuots -> merge_layouts in config validation
• Fix Diff3Ver type annotation (was incorrectly Diff3Hor).

[Copilot]

Pull request overview

This PR addresses several small but impactful correctness issues across Diffview’s highlighting utilities, panel cursor helpers, config validation, and Mercurial revision parsing—primarily fixing incorrect guard logic and improving parsing/validation behavior.

Changes:

• Fix hl.get_style() to return all matching style attributes (comma-separated) instead of only the first match.
• Correct inverted guard conditions in FilePanel/FileHistoryPanel cursor helpers to avoid crashes when buffers aren’t loaded.
• Fix config deprecation/validation issues (deprecated log_options loop break, typo in merge_layouts, and Diff3Ver annotation).
• Tighten Mercurial parse_revs() error checking when exec_sync() fails.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
lua/diffview/vcs/adapters/hg/init.lua	Adjusts parse_revs() error checks when exec_sync() fails.
lua/diffview/scene/views/file_history/file_history_panel.lua	Fixes guard condition for get_item_at_cursor() to prevent crashes.
lua/diffview/scene/views/diff/file_panel.lua	Fixes guard conditions for cursor-based lookup helpers to prevent crashes.
lua/diffview/hl.lua	Fixes style attribute aggregation to return all matching styles.
lua/diffview/config.lua	Fixes deprecated config warning loop and corrects layout validation variable naming typo.
lua/diffview/actions.lua	Fixes Diff3Ver type annotation.

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