Feature request: Support line range syntax in CLI (@file:L1-L10)

Feature Request

Add support for referencing specific line ranges in files directly in the CLI, similar to how the VS Code extension supports @file#lines.

Proposed Syntax

@src/config.ts:50-70

or

@src/config.ts#L50-L70

Use Case

When working in the terminal, it would be helpful to reference specific lines of a file without having to describe them in natural language or copy/paste the code.

Currently, the VS Code extension supports this with @file#lines syntax and keyboard shortcuts, but CLI users don't have an equivalent native feature.

Current Workaround

• Mention lines in natural language: "look at lines 50-70 of src/config.ts"
• Copy and paste the relevant code snippet
• Reference the entire file with @file

Expected Behavior

The CLI should parse the line range syntax and automatically read only the specified lines, providing them as context to the conversation.

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Suggested by a CLI user who prefers terminal workflows over IDE extensions.