Release server/v0.9.0

• Support for custom models, model packs, and default models (see CLI 0.9.0 release notes for details).
• Better accuracy for updates to existing files.
• Plandex is less likely to screw up braces, parentheses, and other code structures.
• Plandex is less likely to mistakenly remove code that it shouldn't.
• Plandex is now much better at working through very long plans without skipping tasks, repeating tasks it's already done, or otherwise losing track of what it's doing.
• Server-side support for plandex diff command to show pending plan changes in git diff format.
• Server-side support for archiving and unarchiving plans.
• Server-side support for plandex summary command.
• Server-side support for plandex rename command.
• Descriptive top-line for plandex apply commit messages instead of just "applied pending changes".
• Better message in plandex log when a single piece of context is loaded or updated.
• Fixes for some rare potential deadlocks and conflicts when building a file or stopping astream.