feat: add alias display for Agent nodes in web UI (#135)

[a-yeyang]

Summary

Closes #135

The MAS visualization currently displays each node's name (e.g. master_agent,
file_agent), which is a code-level identifier and not very user-friendly,
especially for non-English business users.

This PR introduces an optional alias field — a display-only human-friendly
name rendered in the web UI organization tree, while name remains the sole
functional identifier throughout the system.

Usage

oxy.ReActAgent(
    name="calc_agent",      # functional identifier (unchanged)
    alias="计算专家",        # display name shown in the web UI
    ...
)

Changes

File | Change -- | -- oxygent/oxy/base_oxy.py | Add optional alias field on the Oxy base class, inherited by all agents/tools/LLMs oxygent/mas.py | Include alias in the organization tree nodes (init_agent_organization), falling back to name when unset oxygent/web/index.html | Org-tree template renders alias \|\| name; the real name is kept as a hover tooltip for debugging

7 insertions, 2 deletions — no new dependencies.

Design notes

alias is deliberately presentation-layer only. The following keep using
name, so behavior is fully backward compatible:

• LLM-facing tool descriptions and tool-call routing (oxy_request.call)
• Permission lists (sub_agents / permitted_tool_name_list)
• ES trace records (caller / callee) and session names
• The chat "@agent" mention list (functional: clicking invokes by name)

Nodes without an alias fall back to name, so existing projects render
exactly as before.

Testing

• Verified /get_organization returns alias for configured nodes and
  falls back to name for others.
• Smoke-tested end-to-end with a 3-agent / 4-tool MAS: org tree shows
  aliases (see screenshot), hover shows the real name, and a multi-step
  query (master → text_agent, master → calc_agent) completes correctly —
  call chains and traces are unaffected.

Possible follow-ups (out of scope)

• Show alias (name) in the node inspector / playground panels (debug views,
  arguably better with real names — open to discussion)
• Alias mapping for MCP-discovered tools (names come from the MCP server)