Add built-in HTTP Language Server with interactive request execution

[dreygur]

Summary

• Adds a built-in Language Server (http-lsp) that enables executing HTTP requests directly from the editor
• Implements inlay hints, code actions, and hover providers for interactive HTTP request handling
• No external tools required - works out of the box with reqwest HTTP client

Features

• Inlay Hints: Visual inline buttons (▶ Send | 👁 Show | 💾 Save | ◉ Headers)
• Code Actions: Access commands via Ctrl+. / Cmd+. anywhere in a request block
• Hover Info: View request details and cached response status
• Response Caching: Re-display responses without re-executing requests
• Save Response: Execute and save response to file

Technical Details

• http-lsp/ - New Rust LSP crate using tower-lsp
• tree-sitter-http - Bundled parser for .http file parsing
• reqwest - HTTP client for request execution
• Code lens implementation included (awaiting Zed support - Issue #11565)

Setup Required

Users need to enable inlay hints in settings:

  {
    "languages": {
      "http": {
        "inlay_hints": {
          "enabled": true
        }
      }
    }
  }

Test Plan

• Open a .http file with HTTP requests
• Verify inlay hint buttons appear on request lines
• Place cursor on request, press Ctrl+./Cmd+., select "Send Request"
• Verify response displays correctly
• Test "Show Response" displays cached response
• Test "Save Response" saves to file
• Test "Show Headers" displays headers only