[FEATURE]: Built-in File Explorer Panel #36512

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Feature Request

1. Built-in File Explorer Panel

Problem: When working on a codebase, there's no way to browse the project's file structure within the OpenCode interface. Users are forced to switch to a separate file manager or terminal to navigate files, which breaks the workflow.

Proposed Solution: Add a collapsible file explorer panel alongside the main chat/terminal view, similar to VS Code's sidebar. It should support:

• Tree-view of the project directory
• Expand/collapse folders
• Click to open a file in the editor or preview
• Search/filter files by name
• Show file icons based on extension

Use Case: When the agent is editing multiple files or I need to understand the project structure, having a file explorer right in the UI would save a lot of context switching.

2. Clickable File References in Agent Output

Problem: When the agent references a file (e.g., lib/main.dart:42 or src/components/Button.tsx), it's just plain text. There's no way to click on it and jump directly to that file or see it in context.

Proposed Solution: Make file path references in the agent's output clickable. When clicked:

• If a file explorer panel exists → highlight and navigate to the file in the tree
• If a preview/editor exists → open the file at the referenced line number
• If neither exists → at least show a tooltip with the full path and option to copy it

Use Case: The agent often says things like "I modified lib/classes/statics.dart:25" — being able to click that and instantly see the file would significantly improve navigation speed.