[FEAT] S6: lsp_hover tool — type info + docs at position via LSP

[four-bytes-robby]

Purpose

Build the lsp_hover tool for Wave S6 (IDE Integration). Gets type information and documentation for a symbol at a given file position using LSP.

Implementation Plan

1. Create src/tools/lsp-hover.ts — tool implementation
2. Register in src/four-opencode-supertools.ts
3. Write tests covering: mock LSP server, no-server fallback, file-not-found, no-hover-info, doc truncation

Tool Definition

• Name: lsp_hover
• Permission: read
• Args: file_path (string, required), line (number, required), character (number, optional, default 1)

Output Schema

```ts
interface LspHoverOutput {
available: boolean
file: string
position: { line: number; character: number }
type?: string
documentation?: string
fullContents?: string
hint?: string
}
```

Edge Cases

• No LSP server for language → { available: false, hint, suggestion }
• Server timeout → graceful degradation
• File not found → clear error
• No hover info at position → { available: true, type: \"no information at this position\" }
• Long documentation → truncate at 2000 chars with "…truncated" note