feat: add ThePrimeagen/99 AI agent plugin

- Configured with OpenCodeProvider (default, matches opencode environment)
- blink.cmp as completion source for # rules and @ file references
- tmp_dir = ./tmp (per-project, keeps opencode permission happy)
- Auto-injects AGENT.md files from file location up to project root
- Keymaps under <leader>9 group:
    9v (visual) replace selection with AI result
    9s search project → quickfix list
    9x stop all in-flight requests
    9c clear previous results
    9l view debug logs
    9m telescope model picker
    9p telescope provider picker
- Added AI [9]9 group to which-key

lua/plugins/extras/ai.lua

@@ -0,0 +1,56 @@
+-- lua/plugins/extras/ai.lua
+-- ThePrimeagen/99 — AI agent for Neovim
+-- Augments coding via opencode (default provider) with two core workflows:
+--   search  → AI project-wide search, results in quickfix list
+--   visual  → replace visual selection with AI-generated result
+-- https://github.com/ThePrimeagen/99
+
+return {
+  'ThePrimeagen/99',
+  config = function()
+    local _99 = require '99'
+    local basename = vim.fs.basename(vim.uv.cwd())
+
+    _99.setup {
+      -- OpenCodeProvider is the default; matches the opencode environment
+      logger = {
+        level          = _99.DEBUG,
+        path           = '/tmp/' .. basename .. '.99.debug',
+        print_on_error = true,
+      },
+      -- tmp_dir must be inside CWD so opencode has write permission
+      tmp_dir = './tmp',
+      -- Auto-inject AGENT.md files found between the open file and project root
+      md_files = { 'AGENT.md' },
+      completion = {
+        source = 'blink', -- blink.cmp is your completion engine
+      },
+    }
+
+    -- Visual selection → AI replacement
+    -- Intentionally v-mode only: avoids accidentally using a stale selection
+    vim.keymap.set('v', '<leader>9v', _99.visual, { desc = 'AI: replace visual selection' })
+
+    -- Project-wide AI search → quickfix list
+    vim.keymap.set('n', '<leader>9s', _99.search, { desc = 'AI: search project' })
+
+    -- Cancel all in-flight requests
+    vim.keymap.set('n', '<leader>9x', _99.stop_all_requests, { desc = 'AI: stop all requests' })
+
+    -- Clear previous search/visual results
+    vim.keymap.set('n', '<leader>9c', _99.clear_previous_requests, { desc = 'AI: clear previous requests' })
+
+    -- View debug logs for the last run
+    vim.keymap.set('n', '<leader>9l', _99.view_logs, { desc = 'AI: view logs' })
+
+    -- Telescope: switch model on the fly (persists for the session)
+    vim.keymap.set('n', '<leader>9m', function()
+      require('99.extensions.telescope').select_model()
+    end, { desc = 'AI: select model' })
+
+    -- Telescope: switch provider (OpenCode / Claude / Cursor / Gemini)
+    vim.keymap.set('n', '<leader>9p', function()
+      require('99.extensions.telescope').select_provider()
+    end, { desc = 'AI: select provider' })
+  end,
+}

lua/plugins/which-key.lua

@@ -24,6 +24,7 @@ return {
       { '<leader>t', group = '[T]oggle' },
       { '<leader>h', group = 'Git [H]unk', mode = { 'n', 'v' } },
       { '<leader>d', group = '[D]ebug' },
+      { '<leader>9', group = 'AI [9]9' },
     },
   },
 }