fix(inline): preserve syntax fg on added text in diff1_inline

[dlyongemallo]

No description provided.

[Copilot]

Pull request overview

This PR adjusts diff1_inline intraline-added highlighting so added text preserves syntax foreground colors by switching from DiffviewDiffText to a new DiffviewDiffAddInline highlight group (bg/style only).

Changes:

• Switch intraline “added range” extmarks in diff1_inline rendering to use DiffviewDiffAddInline.
• Add/derive the new DiffviewDiffAddInline highlight group from DiffviewDiffAdd while omitting fg.
• Update functional tests to look for the new extmark highlight group and add a highlight-definition test.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
lua/diffview/tests/functional/inline_diff_spec.lua	Updates extmark expectations to DiffviewDiffAddInline and adds a highlight inheritance test.
lua/diffview/scene/inline_diff.lua	Changes intraline added-span extmarks to use DiffviewDiffAddInline.
lua/diffview/hl.lua	Simplifies hi_link() relinking behavior and introduces/updates derived diff highlight groups including DiffviewDiffAddInline.

Comments suppressed due to low confidence (2)

lua/diffview/tests/functional/inline_diff_spec.lua:351

• This overleaf test now asserts DiffviewDiffAddInline extmarks, but the test name/message above still says “DiffText”. Update the wording to match the new highlight group so failures are easier to interpret.

      local ranges = char_ranges(extmarks(bufnr))
      assert.is_true(#ranges > 0, "expected DiffviewDiffAddInline extmarks on added chars")
    end)

lua/diffview/tests/functional/inline_diff_spec.lua:946

• In this helper the highlight group filter was updated to DiffviewDiffAddInline, but several assertion messages in this describe block still mention “DiffText”. Consider updating those strings to the new group name to avoid confusion when diagnosing failures.

      local out = { hl = 0, inline = 0 }
      for _, m in ipairs(marks) do
        local d = m[4]
        if d.hl_group == "DiffviewDiffAddInline" then
          out.hl = out.hl + 1

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.