Use first user prompt for web history conversation titles

[nmaguiar]

Motivation

• History list titles were drifting to later prompts in an ongoing conversation, making entries less representative of the original user request.
• Keep history titles stable and meaningful by using the conversation's first user prompt when available.

Description

• Added extractFirstUserPromptFromEvents(events) to return the first 👤/user message from saved conversation events.
• Updated history rendering in refreshHistoryPanel to derive title from the first user prompt (with safe fallbacks to entry.prompt, entry.title, or 'Conversation').
• Updated addConversationToHistory to anchor stored prompt/title to the first user prompt when present so persistence no longer overwrites the canonical title with later prompts.

Testing

• Verified code changes and locations with rg searches for the new helper and title derivation in public/index.md and inspected the git diff for the file. (succeeded)
• Attempted to run repository tests with ojob tests/miniAUtils.yaml but the ojob command is not available in this environment (failed to run automated tests).
• Served the web UI with python3 -m http.server 8000 from public/ and captured a UI screenshot using a Playwright script to validate the history panel rendering, producing an artifact at browser:/tmp/codex_browser_invocations/.../artifacts/artifacts/history-title-change.png (succeeded).