chore: scope changelog + bugbot to breaking changes only

.cursor/BUGBOT.md

@@ -2,10 +2,16 @@
 
 ## Changelog Enforcement
 
-Any PR that modifies configuration structures or usage patterns must update `CHANGELOG.md`. This includes changes to config fields (added, removed, renamed, moved, or default value changes) in:
+Any PR that introduces **breaking** configuration changes must update `CHANGELOG.md`. Breaking changes are those that require users to update existing configs:
 
-- `src/prime_rl/*/config.py`
-- `src/prime_rl/rl.py`
-- `src/prime_rl/utils/config.py`
+- **Renamed** config fields (old name no longer accepted)
+- **Removed** config fields (field deleted or moved to a different path)
+- **Moved** config fields (field relocated in the config hierarchy)
 
-If such changes are detected without a corresponding `CHANGELOG.md` update, request that the author add an entry.
+Additive changes (new fields with defaults, new optional features) and default value changes do **not** require a changelog entry.
+
+Config files live in:
+
+- `src/prime_rl/configs/`
+
+If breaking changes are detected without a corresponding `CHANGELOG.md` update, request that the author add an entry.

CHANGELOG.md

@@ -1,6 +1,6 @@
 # Changelog
 
-Documenting changes which affect configuration usage patterns (added/moved/removed/renamed fields, notable logic changes).
+Documenting **breaking** configuration changes — renamed, removed, or moved fields that require users to update existing configs.
 
 - **`log.file` and `log.env_worker_logs` removed**: Removed `log.file` (from `LogConfig` and `SharedLogConfig`) and `log.env_worker_logs` (from `LogConfig`). Python file logging is replaced by deployment-level capture. Existing configs using these fields must delete them. Log paths unified: `.stdout` files renamed to `.log`, SLURM logs moved from `slurm/` to `logs/`. (2026-03-31)
 - **`trainer.log.ranks_filter` (NEW)**: Added `ranks_filter: list[int]` to `TrainerLogConfig` (default: `[0]`). Controls which ranks appear in trainer console output via torchrun's `--local-ranks-filter`. (2026-03-31)