feat(sandbox): ship the MCP tool catalog as mcp-tools.json

Problem

Clients that build their own tools from agent-browser, such as the eve extension, hand-write schemas and descriptions that drift from the CLI. They cannot run tools/list when they define their tools, because the CLI lives in a sandbox that does not exist yet.

Changes

• @agent-browser/sandbox/mcp-tools.json: every MCP tool (156) with title, description, input schema, annotations and startup profiles, in tools/list shape
• Generated from the CLI's own definitions by pnpm mcp-tools:sync; the Rust test mcp_tool_catalog_snapshot_is_current fails while the committed file is out of date, so MCP tool changes show up as a reviewable diff in the same PR
• Sandbox README documents the file and mcp call

Stacked on #2238.

Visual proof

cargo test --bin agent-browser mcp_tool_catalog_snapshot: 1 passed. import("@agent-browser/sandbox/mcp-tools.json") from @agent-browser/eve: 156 tools, 29 in core.