chore: bump version to 2.39.1 [skip ci]

feat: inline (unified) diff layout with treesitter syntax highlighting (

#281)

## Summary

Add a new inline diff layout as an alternative to side-by-side. Deleted
lines appear as virtual line overlays with treesitter syntax
highlighting, providing a VSCode-style unified diff experience.

Set `diff.layout = "inline"` to enable. Default remains `"side-by-side"`
— no breaking changes.

## Features

- **Inline diff rendering** — single-window layout with deleted lines as
`virt_lines` overlays
- **Treesitter syntax highlighting** on virtual lines — deleted code
retains keyword, string, function colors merged with diff backgrounds
- **Character-level diff highlights** on both virtual lines (deleted)
and real lines (inserted)
- **Full mode support** — works with standalone, explorer, and history
modes
- **Shared keymaps** — `do` reverts hunk to original, `dp` is no-op
(buffer already has modified content), navigation/textobject/staging all
work
- **44 new tests** covering all inline scenarios with 0 regressions

## Changes

### New files
- `lua/codediff/ui/inline.lua` — core renderer (virt_lines, char
highlights, treesitter syntax)
- `lua/codediff/ui/view/inline_view.lua` — inline engine
(create/update/rerender/show_single_file)
- `tests/ui/inline_spec.lua` — 10 renderer unit tests
- `tests/ui/inline_syntax_spec.lua` — 8 treesitter syntax tests
- `tests/ui/view/inline_standalone_spec.lua` — 14 standalone view tests
- `tests/ui/view/inline_explorer_spec.lua` — 4 explorer mode tests
- `tests/ui/view/inline_history_spec.lua` — 4 history mode tests
- `tests/ui/view/inline_interaction_spec.lua` — 12 interaction tests
(nav, do, autoscroll, textobject, lifecycle)

### Modified files (additive, gated by `layout == "inline"`)
- `config.lua` — `layout = "side-by-side"` option
- `view/init.lua` — router dispatches to inline engine
- `keymaps.lua` — layout-aware do/dp/find_hunk_at_cursor
- `navigation.lua` — inline uses modified line numbers
- `auto_refresh.lua` — inline render branch
- `lifecycle/cleanup.lua` — threshold for inline sessions
- `lifecycle/state.lua` — inline namespace clear + resume render
- `explorer/render.lua` — A/D/?? routing to inline_view.show_single_file
- `history/render.lua` — A/D routing to inline_view.show_single_file

## Usage

```lua
require('codediff').setup({
  diff = { layout = 'inline' },
})
```

## Testing
- 44 new inline-specific tests
- All existing tests pass (5 made layout-resilient)
- Full suite passes with both `inline` and `side-by-side` as default

feat: add close_on_open_in_prev_tab option for gf keymap (#280)

## Summary

When enabled, pressing `gf` closes the codediff tab after opening the
file in the previous tab. Default is `false` (existing behavior
preserved).

Closes #276

## Changes

- **config.lua**: Added `close_on_open_in_prev_tab = false` option under
`keymaps.view`
- **keymaps.lua**: After `open_in_prev_tab` navigates to the file,
optionally closes the diff tab
- **README.md**: Documented new option
- **doc/codediff.txt**: Updated vimdoc

## Usage

```lua
require('codediff').setup({
  keymaps = {
    view = {
      close_on_open_in_prev_tab = true,
    },
  },
})
```

refactor: view engine extraction + single-pane display for A/D/?? fil…

…es (#279)

## Changes

### Refactor: View engine extraction
- Split `view/init.lua` (832 lines) into three focused modules:
  - `view/init.lua` (47 lines): thin router
  - `view/side_by_side.lua`: side-by-side diff engine
  - `view/panel.lua`: shared explorer/history panel setup
- Pure code move, no behavior change

### Feature: Single-pane display for added/deleted/untracked files
- Close the empty pane instead of shrinking it to 1px when a file only
exists on one side
- Handles all modes: explorer (staged/unstaged/two-revision) and history
- Layout manager properly sizes the remaining pane
- 9 new layout test cases (Cases 10-18)
- Consolidates 4 show_* functions into one `show_single_file()` core

### Testing
- All existing tests pass (0 regressions)
- 25 layout tests total (16 existing + 9 new)

fix: defer heavy module loading for faster startup (#272) (#275)

## Summary

Reduces codediff.nvim's startup impact from **~15ms to ~0.6ms** (96%
reduction) by deferring heavy module loading until the user first
invokes `:CodeDiff`.

Closes #272

## Problem

`plugin/codediff.lua` eagerly loaded 42 Lua modules + a C library via
FFI at startup, even when the user never used any diff functionality.
This consumed ~15ms on cold start and ~8ms on warm start.

### Before (startup profiling)
```
       startup: 48.9

codediff.lua            19.42   39.75 ███████████▊
codediff.ui             18.75   38.38 ███████████▌
codediff.ui.view        18.38   37.62 ███████████▎
codediff.ui.explorer     2.12    4.33 █▎
codediff.ui.auto_refresh 1.75    3.57 █
codediff.core.diff       1.09    2.24 ▌
```

### After
```
       startup: 7.3

codediff.lua             0.58    7.92 ██▎
codediff.ui.highlights   0.31    4.32 █▎
codediff.config          0.18    2.47 ▌
codediff.core.virtual_file 0.09  1.20 ▎
```

## Changes

- **`plugin/codediff.lua`**: Replace 4 eager top-level `require()` calls
with 2 lightweight ones (`codediff.ui.highlights` +
`codediff.core.virtual_file`). Wrap the `:CodeDiff` command handler to
lazy-load `codediff.commands` on first invocation.
- **`plugin/vscode-diff.lua`**: Lazy-wrap the `:VscodeDiff` command
handler.
- **`lua/codediff/ui/init.lua`**: Remove eager `lifecycle.setup()` call
(was registering global autocmds at startup).
- **`lua/codediff/ui/view/init.lua`**: Add once-guard to call
`lifecycle.setup()` on first `view.create()`, so cleanup autocmds are
only registered when actually needed.

## What loads at startup (~0.6ms)
- `codediff.ui.highlights` — highlight group definitions
- `codediff.core.virtual_file` — `codediff://` URL scheme registration
- Command registration (negligible)

## What's deferred to first `:CodeDiff` invocation
- C diff library (FFI + `ffi.load()`)
- Explorer, History, Conflict UI modules
- Lifecycle autocmds (`WinClosed`/`TabClosed`/`BufEnter`)
- Git operations module
- View keymaps, navigation, layout

## Testing

- ✅ All plenary tests pass (37 files, 0 failures)
- ✅ E2E validation: `:CodeDiff file`, `:VscodeDiff`, lifecycle cleanup,
multi-tab all work
- ✅ 5 profiling runs confirm consistent ~0.6ms startup

chore: bump version to 2.35.1 [skip ci]

feat: restore file to comparison revision (#274)

## Summary

Closes #270

When comparing against a specific commit (e.g. `origin/HEAD`, a commit
hash), the restore action (`X`) now reverts the file to that revision
instead of the index version. This matches diffview.nvim's behavior.

### Changes

- Added optional `source` parameter to `git.restore_file()` with
backward compatibility for existing callers
- Explorer actions now pass `base_revision` as the source revision
- 6 new tests for restore_file with/without source revision

### Testing

- All existing tests pass
- 6 new restore tests (all pass)

feat(ui): add 3do conflict viewer (#252)

This is a pull request that adds config parameters to where the 3-way
diff view would spawn the current state window.

Originally, we could only do it at the bottom with a fixed height.

- Add another mode for putting the current state of the conflicting file
in center.
- Add configuration parameters where we can now spawn the window at the
center or configure the bottom window height.

## Notes
It would be nicer if we could do these configuration parameters in a
table, but it would kind of break the current config format for that
section.

feat: hunk textobject (ih) (#269)

## Summary

Adds `ih` textobject for diff hunks, enabling standard Vim operations on
hunks:
- `vih` — select hunk
- `yih` — yank hunk
- `dih` — delete hunk
- `cih` — change hunk

Works in both operator-pending and visual modes on diff buffers. Uses
existing `find_hunk_at_cursor()` infrastructure. Configurable via
`keymaps.view.hunk_textobject`.

Closes #144

Merge branch 'dev'