0.21.0

Fixes abound!

• #2200 send prompt cache key for better caching (should improve token efficiency!)
• #2202 split multiline commands to improve readability
• #2095 Parse exec commands and format them more nicely in the UI
• #2186 recognize applypatch command as apply_patch command string
• #2183 Include output truncation message in tool call results to tell the model when it did not get the full output from a command that it might have expected
• #2162 show feedback message after /compact command, fixing an issue when no deltas were sent
• #2050 show diff preview for apply_patch
• #1975 add JSON schema sanitization for MCP tools to ensure compatibility with internal JsonSchema enum external contributor: Thanks @yaroslavyaroslav!