docs: update agent-browser install docs for npx-based resolution

Root `npm install` no longer installs agent-browser (it's not a root
package.json dependency anymore, see #43564) -- update docs that told
users to run it for that purpose, or that credited it with installing
"browser tools".

- browser.md: agent-browser resolves automatically via npx; a global
  npm install -g is now presented as an optional way to skip the
  one-time npx fetch, not a required step.
- browser-provider-plugin.md: fix stale comment claiming post_setup
  "agent_browser" installs the npm dep -- it only ensures Chromium now.
- CONTRIBUTING.md: relabel the two optional `npm install` steps as
  docs-site/workspace dependencies rather than "browser tools".
- termux.md: drop the now-pointless `npm install` from the manual
  Node-dependencies step; Node.js itself is the only prerequisite,
  agent-browser resolves lazily via npx same as everywhere else.

CONTRIBUTING.md

@@ -130,7 +130,7 @@ cd "${HERMES_HOME:-$HOME/.hermes}/hermes-agent"
 # Add dev/test extras on top of the standard install.
 uv pip install -e ".[all,dev]"
 
-# Optional: browser tools / docs site dependencies.
+# Optional: docs site + workspace dependencies.
 npm install
 ```
 
@@ -167,7 +167,7 @@ export PATH="$VIRTUAL_ENV/bin:$PATH"
 # Install with all extras (messaging, cron, CLI menus, dev tools)
 uv pip install -e ".[all,dev]"
 
-# Optional: browser tools
+# Optional: workspace / docs dependencies
 npm install
 ```
 

website/docs/developer-guide/browser-provider-plugin.md

@@ -126,7 +126,7 @@ def get_setup_schema(self) -> dict:
              "prompt": "My Backend API key",
              "url": "https://mybackend.example"},
         ],
-        "post_setup": "agent_browser",   # auto-installs the agent-browser npm dep
+        "post_setup": "agent_browser",   # ensures local Chromium is installed (agent-browser itself resolves via npx)
     }
 ```
 

website/docs/getting-started/termux.md

@@ -155,11 +155,10 @@ hermes setup
 
 ### Install optional Node dependencies manually
 
-The tested Termux path skips Node/browser bootstrap on purpose. If you want to experiment with browser tooling later:
+The tested Termux path skips Node/browser bootstrap on purpose. If you want to experiment with browser tooling later, the only prerequisite is Node.js — `agent-browser` itself resolves lazily via `npx agent-browser` on first browser-tool use, so there's no separate install step:
 
 ```bash
 pkg install nodejs-lts
-npm install
 ```
 
 The browser tool automatically includes Termux directories (`/data/data/com.termux/files/usr/bin`) in its PATH search, so `agent-browser` and `npx` are discovered without any extra PATH configuration.

website/docs/user-guide/features/browser.md

@@ -472,10 +472,12 @@ AGENT_BROWSER_ARGS=--no-sandbox
 
 ### Install agent-browser CLI
 
+You don't need to install anything — `agent-browser` resolves automatically via
+`npx agent-browser` on first browser-tool use. To avoid the one-time npx fetch,
+you can install it globally ahead of time (optional):
+
 ```bash
 npm install -g agent-browser
-# Or install locally in the repo:
-npm install
 ```
 
 :::info