feat: support multi-vault Codex profile selection

[maehwasoo]

Problem statement

Using multiple Obsidian vaults with AILSS and multiple Codex clients is currently cumbersome.

Each vault MCP service has a different localhost port/token, but the plugin’s copy helper emits a fixed config header ([mcp_servers.ailss]). This makes profile switching manual and error-prone when users want to connect to and interact with a specific vault server.

Proposed solution

Add multi-vault Codex profile support in the Obsidian plugin and docs.

• Add a configurable Codex server alias per vault (e.g., ailss_work, ailss_personal), with a safe default.
• Update “Copy Codex MCP config” to emit [mcp_servers.<alias>] instead of a fixed key.
• Provide a clear workflow for multi-client usage (multiple Codex clients selecting different vault profiles concurrently).
• Document recommended operational setup:
  • unique port/token per vault
  • profile naming convention
  • selection/switching flow in Codex config
• Validation:
  • two or more vault servers can run concurrently without profile key collisions
  • users can select target vault profile in Codex without manual key rewriting each time
  • single-vault default path remains simple and backward-compatible

Constraints / context (optional)

• Keep localhost-first security model and existing token auth.
• Preserve backward compatibility for existing single-vault users.
• This issue does not require remote multi-host orchestration.