docs(help): promote skills to the top of --help so agents discover them first (#1251)

The `Skills:` section was buried between `Setup:` and `Snapshot Options:` in
the top-level `--help`, where an agent skimming the output would pass over it
on the way to flag docs. Move it to a prominent "Start here (for AI agents)"
block directly below `Usage:` so it's the first thing an agent sees, and
reframe the copy so it conveys what skills *are* (workflow patterns, ref
usage, copy-paste examples) rather than just listing subcommand flags.

Skills are the intended entry point for agents. They ship with the CLI,
always version-match the installed binary, and cover both `agent-browser`
core usage and specialized workflows (Electron, Slack, exploratory testing,
cloud browser providers). Surfacing them up front prevents agents from
guessing commands out of flag docs when a hand-written workflow guide is
one command away.

No functional change. Only the ordering and wording of `--help` output.

cli/src/output.rs

@@ -2853,6 +2853,20 @@ agent-browser - fast browser automation CLI for AI agents
 
 Usage: agent-browser <command> [args] [options]
 
+Start here (for AI agents):
+  agent-browser skills get agent-browser --full
+
+  Skills ship with the CLI (always version-matched) and include workflow
+  patterns, ref/selector usage, and copy-paste examples. Prefer this over
+  guessing commands from flag docs alone. Specialized skills cover Electron
+  apps, Slack, exploratory testing, and cloud browser providers.
+
+  skills [list]                List available skills
+  skills get <name>            Get a skill's core content (overview + examples)
+  skills get <name> --full     Include references and templates
+  skills get --all             Get every skill
+  skills path [name]           Print skill directory path
+
 Core Commands:
   open <url>                 Navigate to URL
   click <sel>                Click element (or @ref)
@@ -2972,12 +2986,6 @@ Setup:
   dashboard start            Start the observability dashboard
   profiles                   List available Chrome profiles
 
-Skills:
-  skills [list]              List available skills
-  skills get <name> [--full] Get skill content (--full includes references)
-  skills get --all           Get all skill content
-  skills path [name]         Print skill directory path
-
 Snapshot Options:
   -i, --interactive          Only interactive elements
   -c, --compact              Remove empty structural elements