fix(ci): add changeset file, revert manual version bump

The CI pipeline uses changesets to manage versioning automatically.
Replace the manual 0.21.0 version bump and CHANGELOG entry with a
proper changeset file that the release pipeline will consume.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: konard

js/.changeset/replace-default-model-242.md

@@ -0,0 +1,10 @@
+---
+'@link-assistant/agent': minor
+---
+
+feat: replace deprecated qwen3.6-plus-free default with nemotron-3-super-free (#242)
+
+- Default model changed from `qwen3.6-plus-free` to `nemotron-3-super-free` (~262K context, NVIDIA hybrid Mamba-Transformer)
+- Removed `qwen3.6-plus-free` from compaction models cascade (free promotion ended April 2026)
+- Updated provider priority lists to remove unavailable model
+- Moved `qwen3.6-plus-free` to deprecated/discontinued sections in documentation

js/CHANGELOG.md

@@ -1,16 +1,5 @@
 # @link-assistant/agent
 
-## 0.21.0
-
-### Minor Changes
-
-- feat: replace deprecated qwen3.6-plus-free default with nemotron-3-super-free (#242)
-  - Change default model from `qwen3.6-plus-free` to `nemotron-3-super-free` (~262K context)
-  - Remove `qwen3.6-plus-free` from compaction models cascade (free promotion ended April 2026)
-  - Updated cascade: `(big-pickle minimax-m2.5-free nemotron-3-super-free gpt-5-nano same)`
-  - Move `qwen3.6-plus-free` to deprecated/discontinued sections in documentation
-  - Update provider priority lists to remove unavailable model
-
 ## 0.20.2
 
 ### Patch Changes

js/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@link-assistant/agent",
-  "version": "0.21.0",
+  "version": "0.20.2",
   "description": "A minimal, public domain AI CLI agent compatible with OpenCode's JSON interface. Bun-only runtime.",
   "main": "src/index.js",
   "type": "module",