```markdown
# <type>(<scope>): <concise summary>
# Required.
#
# Purpose:
# - Quickly communicates the intent when scanning `git log`.
# - Follow Conventional Commits for consistency and tooling.
# - Describe the intended outcome, not the implementation.
#
# Examples:
# feat(auth): support OAuth device flow
# fix(cache): prevent stale session reuse
# refactor(api): simplify request validation

## Why
<!--
Explain why this change exists.

This is the most valuable part of the commit because the code diff
already shows WHAT changed. Future maintainers (human or AI) often
need to understand WHY the change was made.

Include, where applicable:
- Problem being solved
- User or business need
- Bug or root cause
- Important context that is not visible in the code

Omit if the reason is immediately obvious.
-->

## Implementation Notes
<!--
Capture decisions that are difficult to infer from the code.

Useful information includes:
- Why this approach was chosen
- Important assumptions or invariants
- Constraints imposed by external systems
- Tradeoffs or intentional compromises
- Non-obvious implementation details
- Workarounds or temporary solutions

Do NOT describe the diff ("renamed X", "added Y", etc.).
The code already documents that.
Omit if there is nothing worth preserving.
-->

## Impact
<!--
Document effects that future developers should know.

Examples:
- Behavior changes
- Breaking changes
- Performance implications
- Security considerations
- Migration or deployment requirements
- Compatibility concerns
- Follow-up work or known limitations

Omit if there are no noteworthy impacts.
-->

---
# References (Git Trailers)
# Structured metadata for traceability and tooling.
# Use only the trailers that apply.

Fixes:
Refs:
ADR:
RFC:
Design:
Co-authored-by:
Reviewed-by:
Signed-off-by:
BREAKING CHANGE:
```