repl: categorize help and centralize LLM checks

- Group `/help` output into Browser, LLM, and Meta commands.
- Only show LLM commands in help if an LLM client is configured.
- Centralize the check for commands requiring an LLM in the REPL loop.
- Add descriptions to meta and LLM commands.

src/agent/Agent.zig

@@ -478,15 +478,16 @@ fn runRepl(self: *Agent) void {
             },
         };
 
+        if (cmd.needsLlm() and self.ai_client == null) {
+            self.terminal.printErrorFmt("/{s} requires an LLM. Drop --no-llm and set an API key (ANTHROPIC_API_KEY, OPENAI_API_KEY, or GOOGLE_API_KEY).", .{@tagName(std.meta.activeTag(cmd))});
+            continue :repl;
+        }
+
         switch (cmd) {
             .comment => continue :repl,
             .login, .acceptCookies => {
-                if (self.ai_client == null) {
-                    self.terminal.printError("/login and /acceptCookies require an LLM. Drop --no-llm and set an API key (ANTHROPIC_API_KEY, OPENAI_API_KEY, or GOOGLE_API_KEY).");
-                    continue :repl;
-                }
-                const prompt = if (cmd == .login) login_prompt else accept_cookies_prompt;
                 const label: []const u8 = if (cmd == .login) "/login" else "/acceptCookies";
+                const prompt = if (cmd == .login) login_prompt else accept_cookies_prompt;
                 _ = self.runTurn(.{ .prompt = prompt, .record_comment = line, .label = label });
             },
             .tool_call => |tc| {
@@ -527,21 +528,33 @@ fn handleVerbosity(self: *Agent, rest: []const u8) void {
     self.terminal.printInfoFmt("verbosity: {s}", .{@tagName(level)});
 }
 
+fn helpLessThan(_: void, a: SlashCommand.Help, b: SlashCommand.Help) bool {
+    return std.mem.lessThan(u8, a.name, b.name);
+}
+
+fn printHelpSection(term: *Terminal, header: []const u8, rows: []SlashCommand.Help) void {
+    if (rows.len == 0) return;
+    std.sort.pdq(SlashCommand.Help, rows, {}, helpLessThan);
+    term.printInfo(header);
+    for (rows) |r| term.printInfoFmt("  /{s} — {s}", .{ r.name, r.description });
+}
+
 fn printSlashHelp(self: *Agent, arena: std.mem.Allocator, target: []const u8) void {
     if (target.len == 0) {
-        self.terminal.printInfo("Slash commands (no LLM, REPL only):");
         const all = Schema.all();
-        const sorted = arena.alloc(*const Schema, all.len) catch {
-            for (all) |s| self.terminal.printInfoFmt("  /{s} — {s}", .{ s.tool_name, firstSentence(s.description) });
-            self.terminal.printInfo("Meta: /help [name], /quit, /verbosity <low|medium|high>");
-            return;
-        };
-        for (sorted, all) |*p, *s| p.* = s;
-        std.sort.pdq(*const Schema, sorted, {}, Schema.lessByName);
-        for (sorted) |s| {
-            self.terminal.printInfoFmt("  /{s} — {s}", .{ s.tool_name, firstSentence(s.description) });
+        const browser = arena.alloc(SlashCommand.Help, all.len) catch return;
+        for (all, browser) |*s, *e| e.* = .{ .name = s.tool_name, .description = firstSentence(s.description) };
+        printHelpSection(&self.terminal, "Browser commands:", browser);
+
+        if (self.ai_client != null) {
+            const llm = arena.alloc(SlashCommand.Help, SlashCommand.llm_commands.len) catch return;
+            @memcpy(llm, &SlashCommand.llm_commands);
+            printHelpSection(&self.terminal, "\nLLM commands:", llm);
         }
-        self.terminal.printInfo("Meta: /help [name], /quit, /verbosity <low|medium|high>");
+
+        const meta = arena.alloc(SlashCommand.Help, SlashCommand.meta_commands.len) catch return;
+        for (SlashCommand.meta_commands, meta) |m, *e| e.* = .{ .name = m.name, .description = m.description };
+        printHelpSection(&self.terminal, "\nMeta commands:", meta);
         return;
     }
     const lookup = if (target[0] == '/') target[1..] else target;

src/agent/SlashCommand.zig

@@ -23,6 +23,13 @@
 
 const std = @import("std");
 
+/// Shared row format for the `/help` listing — `name` is the slash name
+/// (no `/`), `description` is a single-sentence summary.
+pub const Help = struct {
+    name: []const u8,
+    description: []const u8,
+};
+
 pub const MetaCommand = struct {
     tag: Tag,
     name: [:0]const u8,
@@ -31,6 +38,9 @@ pub const MetaCommand = struct {
     hint: []const u8,
     /// Tab-completion candidates for the first positional arg.
     values: []const [:0]const u8,
+    /// First-sentence summary for `/help`; longer detail is rendered by
+    /// `Agent.printSlashHelp` for the per-command lookup.
+    description: []const u8,
 
     /// Dispatched by `Agent.handleMeta` via an exhaustive switch so adding
     /// a new meta command is a compile error until it's wired up there too.
@@ -38,9 +48,17 @@ pub const MetaCommand = struct {
 };
 
 pub const meta_commands = [_]MetaCommand{
-    .{ .tag = .help, .name = "help", .hint = "", .values = &.{} },
-    .{ .tag = .quit, .name = "quit", .hint = "", .values = &.{} },
-    .{ .tag = .verbosity, .name = "verbosity", .hint = "<low|medium|high>", .values = &.{ "low", "medium", "high" } },
+    .{ .tag = .help, .name = "help", .hint = "", .values = &.{}, .description = "Show help for a slash command, or list all when no name is given" },
+    .{ .tag = .quit, .name = "quit", .hint = "", .values = &.{}, .description = "Exit the REPL" },
+    .{ .tag = .verbosity, .name = "verbosity", .hint = "<low|medium|high>", .values = &.{ "low", "medium", "high" }, .description = "Set REPL agent verbosity; bare /verbosity prints the current level" },
+};
+
+/// LLM-driven slash commands. Parsed via `script.Command.parse` (they're
+/// variants of the `Command` union) — listed here only so the help
+/// renderer and completer have a single source of names + descriptions.
+pub const llm_commands = [_]Help{
+    .{ .name = "login", .description = "Log in to the current site using $LP_* env-var credentials" },
+    .{ .name = "acceptCookies", .description = "Find and dismiss the cookie consent banner" },
 };
 
 pub fn findMeta(name: []const u8) ?*const MetaCommand {