feat(layout): add diff1_inline unified diff view

[dlyongemallo]

Single-window layout rendering unified diffs via extmark overlays. Style configurable via view.inline.style ("unified" default; "overleaf" for inline strikethrough deletions). ]c/[c navigate hunks.

Char-level diff helpers adapted from @tienlonghungson's sample in #109, which was modified from YouSame2/inlinediff-nvim.

Closes #108 and #109.

[Copilot]

Pull request overview

Adds a new single-window unified (“inline”) diff layout to Diffview, rendering changes via extmarks/virtual lines and providing inline hunk navigation that works without Neovim’s native diff mode.

Changes:

• Introduces diff1_inline layout plus an inline_diff renderer (unified + “overleaf” style) with cached hunks for ]c/[c navigation.
• Extends layout/file-entry lifecycle to support non-window “owned files” and to clear layout-specific render state during layout conversion.
• Updates config, keymaps, highlights, documentation, and adds functional test coverage for the new renderer/layout.

Reviewed changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
lua/diffview/scene/layouts/diff_1_inline.lua	New diff1_inline layout that renders unified diffs into a single buffer via extmarks.
lua/diffview/scene/inline_diff.lua	New inline diff renderer (unified + overleaf) with hunk caching and navigation helpers.
lua/diffview/config.lua	Registers diff1_inline, adds view.inline.style validation, and adds layout-specific keymaps.
lua/diffview/actions.lua	Adds next_inline_hunk/prev_inline_hunk and centralizes “jump to first change” logic.
lua/diffview/scene/layout.lua	Adds teardown_render(), owned_files(), and get_file_for() to support inline layout lifecycle.
lua/diffview/scene/file_entry.lua	Uses owned_files() for teardown/head updates/activation; calls teardown_render() before layout conversion; uses get_file_for() during conversion.
lua/diffview/hl.lua	Adds DiffviewDiffDeleteInline highlight group for overleaf strikethrough deletions.
lua/diffview/scene/views/diff/listeners.lua	Routes file_open_new behavior through actions.jump_to_first_change.
lua/diffview/scene/views/file_history/listeners.lua	Same file_open_new jump-to-first-change centralization as diff view.
lua/diffview/tests/functional/layouts_spec.lua	Extends layout symbol tests to cover Diff1Inline and teardown render behavior.
lua/diffview/tests/functional/inline_diff_spec.lua	New functional test suite for inline renderer behavior, styles, and hunk navigation.
lua/diffview/tests/functional/file_entry_spec.lua	Tests layout conversion teardown behavior and updates stubs to reflect owned_files().
lua/diffview/tests/functional/cycle_layouts_spec.lua	Adds diff1_inline to known layouts and cycle-layout insertion expectations.
lua/diffview/tests/functional/config_options_spec.lua	Adds validation tests for view.inline.style (default/overleaf/invalid/non-table).
doc/diffview_defaults.txt	Documents defaults for diff1_inline and view.inline.style, plus keymaps.
doc/diffview.txt	Adds user-facing docs for diff1_inline, view.inline, and inline-hunk actions.
TIPS.md	Adds usage tips and configuration examples for inline and overleaf styles.

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[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated no new comments.

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Pull request overview

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Pull request overview

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Pull request overview

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