feat(cli, editor): Allow editing configuration in query editor

[JeanMertz]

Users can now modify the active configuration directly within the QUERY_MESSAGE.md editor when using jp query. The editor displays a subset of the current configuration in a TOML code block below a cut marker, which can be edited (and amended) before submitting the query. Invalid configuration will cause the editor to reopen with an error message, allowing immediate correction.

Currently, the configuration section shows the model ID and reasoning parameters, but any valid configuration properties can be set in this code block. Changes made in the editor are merged with the existing configuration and stored with the conversation message, eliminating the need to close the editor and restart with different CLI arguments.

The editor also shows an improved conversation history section with timestamps, model information, and properly formatted markdown for assistant responses including reasoning content when available.

Implementation adds a new QueryDocument parser in crates/jp_cli/src/editor/parser.rs that handles the structured format of the query file, separating the query content from metadata sections. The edit_query function now returns both the query text and any configuration changes, which are merged into the partial config before storing messages. Error handling includes validation feedback displayed directly in the editor to streamline the correction workflow.

Related: #217