feat(extensions): add Tabby extension for persisting tab names

[ChristophSchmidpeter]

What

Add a new extension that saves and restores Tabby (nanozuki/tabby.nvim)
tab names across sessions. It prefers Tabby’s canonical global
vim.g.TabbyTabNames when present and falls back to querying Tabby’s API
to build a JSON mapping.

Why

Tabby users often assign custom tab names, but those are lost when
restarting Neovim. This extension ensures tab names are preserved
seamlessly with resession.

How

• Save hook: export vim.g.TabbyTabNames or compute a fallback via Tabby’s API.
• Load hook: restore the JSON, refresh the tabline.
• Safety measures:
  • wrap external calls in pcall so loading works if Tabby is absent,
  • only write the global when the JSON differs,
  • trigger a UI refresh (redrawtabline) after restore.

Notes

• No configuration required.
• Fails gracefully when Tabby is not installed.

[Copilot]

Pull Request Overview

Add a new extension for resession.nvim that persists Tabby tab names across session saves and restores. The extension provides fallback mechanisms and safe restoration practices.

• Implements on_save and on_post_load functions for the resession extension API
• Adds fallback logic to compute tab names from Tabby API when global variable is unavailable
• Uses defensive programming with pcall wrappers for safe external library calls

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}

[Copilot]

The restoration unconditionally overwrites vim.g.TabbyTabNames even when the current value might be identical. According to the description, it should 'only write the global when the JSON differs', but there's no comparison with the existing value.

Suggested change

	vim.g.TabbyTabNames = json
	if vim.g.TabbyTabNames ~= json then
	vim.g.TabbyTabNames = json
	end

[Copilot]

The comment refers to 'LSP false positive' but should refer to 'LuaLS false positive' or 'language server false positive' for clarity, since LSP (Language Server Protocol) is the protocol, not the specific tool generating the warning.

Suggested change

	-- LSP false positive: vim.cmd is a callable table, but LuaLS mis-types it as plain table.
	-- LuaLS false positive: vim.cmd is a callable table, but LuaLS mis-types it as plain table.

[stevearc]

Thanks for the PR! For organizational purposes, I think it makes more sense to put these plugin-specific extensions into the plugin repos instead of in resession. The only extensions that resession ships with are for built-in neovim features (colorscheme and quickfix). The resession API is very stable; I think it's only changed once, and it was done in a backwards compatible way, so it's likely better to keep the extension code more tightly coupled with the plugin it supports because it is more likely those will have to change in tandem.