fix(editor): highlight all visible search matches

[bajrangCoder]

No description provided.

[greptile-apps]

Greptile Summary

Adds a viewport-bounded CodeMirror plugin that highlights every visible match for searches driven outside the native search panel.

• Installs the custom highlighter alongside the editor search extension.
• Recomputes decorations when the query, panel, document, selection, or viewport changes.
• Adds unit coverage for query updates, selected matches, viewport bounding, overlapping ranges, and native-panel handoff.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete changed-code defect identified.

The new highlighter is conditionally composed with search support, limits scanning to expanded visible ranges, merges overlapping scan windows, and refreshes decorations for the state transitions that affect matching.

Important Files Changed

Filename	Overview
src/cm/mainEditorExtensions.ts	Registers the custom match highlighter whenever the main CodeMirror search extension is present.
src/cm/searchMatchHighlighter.ts	Implements viewport-scoped search decorations and refreshes them across relevant editor-state transitions.
tests/unit/searchMatchHighlighter.test.ts	Covers the principal decoration, viewport, selection, and panel-handoff behavior introduced by the plugin.

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