Add configurable context window size

[bhouston]

Description

Adds a configuration option to manually specify the context window size in mycoder.config.js.

Changes

• Added contextWindow configuration option to manually specify the context window size
• Updated all LLM providers to use this configuration when a model's context window is not known
• Updated documentation in README.md and docs package
• Added special documentation for Ollama users since they're more likely to need this feature

Motivation

When using models that are not known by the tool (especially with Ollama where there are many possible models), users need a way to manually specify the context window size so that:

1. Token usage tracking can work correctly
2. Automatic compaction can be triggered when appropriate

Related Issues

• Fixes Add configurable context window size #363 (Add configurable context window size)
• Related to Make model context window optional #362 (Make model context window optional)

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"prompt is too long: 200130 tokens > 200000 maximum"}} AnthropicProvider.generateText(anthropic.ts) View Issue
• ‼️ Error: Connection error. AnthropicProvider.generateText(anthropic.ts) View Issue

_{Did you find this useful? React with a 👍 or 👎}