Address 4 P2 review comments on PR #3314:
1. effectiveHideThinkingBlock now uses viewSession.thinkingLevel
instead of session.thinkingLevel — in focused-agent mode, the
viewed transcript may have a different thinking level than the
main session.
2. thinking_level_changed handler now iterates existing
AssistantMessageComponent children and calls setHideThinkingBlock
with the new effective value, then resetDisplay() to repaint.
Previously only new/streaming messages got the updated visibility.
3. Changed AssistantMessageComponent import from type-only to value
import for instanceof check.
4. Agent Hub callback already uses effectiveHideThinkingBlock which
now reflects viewSession — no separate fix needed.
oldschoola
f8ec04871f