Feature Request: Post-File-Edit Hook

Summary

Add a hook that fires after Agentic writes to a file.

Motivation

The existing on_response_complete hook doesn't provide information about which files were modified. I want to auto-format, lint, or post-process edited files.

Proposed Solution

{
  "carlos-algms/agentic.nvim",
  opts = {
    hooks = {
      on_file_edit = function(data)
        -- data.filepath: string - Absolute path to edited file
        -- data.session_id: string - ACP session ID
        -- data.tab_page_id: number - Neovim tabpage ID
        -- data.bufnr: number|nil - Buffer number if loaded
        
        vim.lsp.buf.format({ bufnr = data.bufnr, timeout_ms = 5000 })
      end,
    }
  }
}

Current Workaround

Track all buffer writes with BufWritePost autocmd between on_prompt_submit and on_response_complete, but this captures non-Agentic writes too.