feat(menu): #140 — Ask opens a web chat, provider is in-flake state

Bernardo: "opening claude-code is too disruptive". SUPER+CTRL+A spent a
terminal, an npm fetch and a REPL on "what's the syntax for…" — the prompt
was the right surface, the destination was not. The query is now
URL-encoded into the provider's web chat and handed to xdg-open.

settings.ask.provider (claude|chatgpt|gemini|grok, default claude) with a
Preferences row, read from state at RUN TIME so switching needs no
rebuild, and any unknown/absent value falls back rather than opening
nothing. He asked for chatgpt + grok alongside claude/gemini, and for the
CLI to go: claude-code is deleted and pkgs.nodejs leaves with it (carried
only for that npx). Keybind is "Ask AI" now the destination is the user's.

The failure mode is the design point: prefill is undocumented on all four
vendors, each can drop `?q=` unilaterally, and it fails SILENTLY — you
land in an empty chat having already typed the question. So the query is
also copied to the clipboard (a vendor breaking change costs one paste,
not the question), and the URLs sit in one attrset so the repair is one
line.

Verified against the generated script: bash -n clean; every bad state
value (unset/null/garbage) falls back to claude; a hostile query encodes
correctly (& → %26, ? → %3F, # → %23, $(whoami) neutralised, café →
caf%C3%A9). NOT verified on purpose: whether each vendor fills the box or
auto-submits — that means posting into Bernardo's own accounts.

Sweep: ROADMAP's shipped-modules line described the npx REPL; nix-ld's
comment cited claude-code as its example; both fixed. Menu row + keybind
renamed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/nixos/default.nix

@@ -288,9 +288,9 @@ in
 
     # ── Foreign binaries: nix-ld ─────────────────────────────────────
     # An ld.so shim so dynamically-linked binaries not built for NixOS
-    # (downloaded tools, language servers, pip/npm-installed ELFs, the
-    # npx-fetched claude-code) run without manual patchelf. On by default —
-    # a pragmatic-desktop expectation.
+    # (downloaded tools, language servers, pip/npm-installed ELFs) run
+    # without manual patchelf. On by default — a pragmatic-desktop
+    # expectation.
     programs.nix-ld.enable = lib.mkDefault true;
 
     # ── Firmware ─────────────────────────────────────────────────────