fix(tui): respect display.show_thinking when rendering stored messages (#98)

[quangdang46]

What

stored_message_visible_text (in src/tui/app/state_ui_messages.rs) was concatenating ContentBlock::Reasoning with ContentBlock::Text in a single match arm, ignoring the display.show_thinking setting. Result: providers that emit reasoning_content (MiniMax, OpenRouter routing through Kimi/Qwen, Gemini's thinking blocks via the openrouter SSE path) leaked the chain-of-thought into the visible transcript even when the user had explicitly set show_thinking=false in their config.

This addresses issue #98: #98

Changes

• src/tui/app/state_ui_messages.rs:
  • Split the match arm so Reasoning blocks are gated by crate::config::config().display.show_thinking.
  • Extracted the inner pure logic into stored_message_visible_text_with_show_thinking(message, show_thinking) so tests can pin the decision deterministically without mutating the global config.
• 3 regression tests:
  • reasoning_block_hidden_when_show_thinking_is_false (the bug)
  • reasoning_block_shown_when_show_thinking_is_true
  • empty_reasoning_block_is_skipped_either_way (covers both polarities)

Tests

$ cargo test -p jcode --lib show_thinking_tests
test result: ok. 3 passed; 0 failed

Notes

The streaming path already respects show_thinking (src/agent/turn_streaming_*.rs, src/tui/app/turn.rs:655). The bug was specifically in the rendering of already-stored messages — i.e. session reload, scrollback re-render, and any code path that goes through stored_message_visible_text.