Add projection and paging controls to outline output

[Widthdom]

Problem

outline --json can emit very large payloads for large files, which makes dogfood audits and agent workflows harder to drive. Users need a way to request just the symbols, fields, or page they intend to inspect.

Evidence

• Running outline against src/CodeIndex/Lsp/LspServer.cs with JSON output produced an extremely large result for one file.
• Search already has projection-oriented controls such as result fields; outline does not expose an equivalent bounded workflow.

Suggested fix

• Add outline field projection, symbol-kind filters, and/or paging controls.
• Include total counts and next-cursor metadata for machine-readable output.
• Keep the default human output useful while making JSON output safe for large files and agents.

[Widthdom]

Work started on branch fix-issue3986.