* fix: change compact_context default to true
Local LLMs with limited context windows immediately run out of context
when compact_context defaults to false. The system prompt alone can
consume 25K+ tokens, exceeding even 55K context windows with history.
Setting compact_context=true by default limits system prompt injection
to 6000 chars and RAG results to 2 chunks, making the agent usable
with smaller models out of the box.
Fixes#3987
* docs: update compact_context default to true in config reference
Update all locale variants (en, zh-CN, vi) to reflect the new default.
* test: update tests to expect compact_context default of true
Update assertions in schema.rs unit tests and config_persistence.rs
component tests to match the new default value.
95bf229225