refactor: remove browser_close tool — auto-cleanup handles it

The browser_close tool was called in only 9% of browser sessions (13/144
navigations across 66 sessions), always redundantly — cleanup_browser()
already runs via _cleanup_task_resources() at conversation end, and the
background inactivity reaper catches anything else.

Removing it saves one tool schema slot in every browser-enabled API call.

Also fixes a latent bug: cleanup_browser() now handles Camofox sessions
too (previously only Browserbase). Camofox sessions were never auto-cleaned
per-task because they live in a separate dict from _active_sessions.

Files changed (13):
- tools/browser_tool.py: remove function, schema, registry entry; add
  camofox cleanup to cleanup_browser()
- toolsets.py, model_tools.py, prompt_builder.py, display.py,
  acp_adapter/tools.py: remove browser_close from all tool lists
- tests/: remove browser_close test, update toolset assertion
- docs/skills: remove all browser_close references

website/docs/reference/tools-reference.md

@@ -20,7 +20,6 @@ In addition to built-in tools, Hermes can load tools dynamically from MCP server
 |------|-------------|----------------------|
 | `browser_back` | Navigate back to the previous page in browser history. Requires browser_navigate to be called first. | — |
 | `browser_click` | Click on an element identified by its ref ID from the snapshot (e.g., '@e5'). The ref IDs are shown in square brackets in the snapshot output. Requires browser_navigate and browser_snapshot to be called first. | — |
-| `browser_close` | Close the browser session and release resources. Call this when done with browser tasks to free up Browserbase session quota. | — |
 | `browser_console` | Get browser console output and JavaScript errors from the current page. Returns console.log/warn/error/info messages and uncaught JS exceptions. Use this to detect silent JavaScript errors, failed API calls, and application warnings. Requi… | — |
 | `browser_get_images` | Get a list of all images on the current page with their URLs and alt text. Useful for finding images to analyze with the vision tool. Requires browser_navigate to be called first. | — |
 | `browser_navigate` | Navigate to a URL in the browser. Initializes the session and loads the page. Must be called before other browser tools. For simple information retrieval, prefer web_search or web_extract (faster, cheaper). Use browser tools when you need… | — |