docs: use placeholder PR number in context-window changelog entry

Real PR number to be filled in once the PR is opened.

Author: jsourcebot

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - Added per-step token cost tracking and estimated tool call token usage to Ask Sourcebot chat history. [#1353](https://github.com/sourcebot-dev/sourcebot/pull/1353)
-- Added a context-window usage gauge to the Ask Sourcebot chat details, showing how much of the selected model's context window each turn occupies. Window sizes are resolved from the models.dev catalog. [#1370](https://github.com/sourcebot-dev/sourcebot/pull/1370)
+- Added a context-window usage gauge to the Ask Sourcebot chat details, showing how much of the selected model's context window each turn occupies. Window sizes are resolved from the models.dev catalog. [#XXXX](https://github.com/sourcebot-dev/sourcebot/pull/XXXX)
 
 ### Fixed
 - Send anonymous server-side PostHog events as personless so unauthenticated requests don't inflate person counts. [#1367](https://github.com/sourcebot-dev/sourcebot/pull/1367)