Fix keymap collision on <leader>j/<leader>k (now resize-only;
location-list moved to ]l/[l). Migrate diagnostic signs from
deprecated vim.fn.sign_define to vim.diagnostic.config. Drop
orphan after/nvim-tree.lua and the bogus require("../current-theme").
Add foundation snacks.nvim spec. Remove playground, vim-maximizer,
poet-v, git-blame, render-markdown, and all five AI plugin specs.
Enable gitsigns current_line_blame.
David Ibia