fix(chat): load message history on first conversation click

PR #730 — Closes #729

Bug

First conversation click from clean state shows empty placeholder instead of messages

Root Cause

skipNextHistoryRef unconditionally set on empty→non-empty transition, skipping loadHistory()

Fix

Guard skip with expectingRunRef.current — only active during new-chat send flow

Same instance (claw:3000 backend), same user (kai/Master), same agent (glm thục bô), same conversation (Chat a95c8ffa), light theme. Callout borders mark the review area.

Chat — First Click from Clean State

BEFORE
Before: empty placeholder on first click

Before: Clicking "Chat a95c8ffa" from initial state — conversation highlighted but main area shows "Start a conversation" placeholder. Messages never load.

AFTER
After: messages load on first click

After: Same click — conversation messages load immediately. The 5-message history is displayed correctly on first click.