## Why

The CLI's CODEOWNERS catch-all assigns 6 people to every PR outside a
few narrow paths. This creates review noise and diffuses responsibility.
We want targeted reviewer suggestions based on who actually worked on
the changed code recently.

## Changes

Before: Every PR touching core code auto-assigns all 6 CODEOWNERS. No
signal about who is best suited to review.

Now: A new GitHub Action analyzes git history of the changed files and
posts a PR comment with two sections:
- **Suggested reviewers** (1-3 people best suited based on
recency-weighted git history)
- **Eligible reviewers** (everyone from CODEOWNERS who could review,
minus the suggested ones)

This is additive only. CODEOWNERS and auto-assign stay unchanged.

How it works:
- Triggers on PR open, synchronize, and ready-for-review (skips drafts
and fork PRs)
- Classifies changed files by type (source=1.0, tests=0.3,
acceptance=0.2, generated=0.0)
- Scores contributors using recency-weighted commit history (half-life
150 days)
- Resolves git author names to GitHub logins via the GitHub API (no
hardcoded alias table to maintain)
- Parses `.github/CODEOWNERS` to find eligible reviewers for the changed
paths
- Updates the comment in-place on re-runs (no notification churn)

Implementation: a single Python script (`tools/suggest_reviewers.py`,
281 lines) and a minimal workflow YAML.

## Test plan

- [x] Action ran on this PR itself and posted a comment successfully
- [x] Verified script parses cleanly, passed `make checks`, passed `ruff
format`
- [x] Dry-run tested against 4 recent merged PRs with different
characteristics:

**PR #4784** (66 files, by pietern, big DABs rename):
```
## Suggested reviewers
- @denik -- recent work in `./`, `bundle/`, `cmd/bundle/generate/`
Confidence: high

## Eligible reviewers
@andrewnester, @anton-107, @lennartkats-db, @shreyas-goenka, @simonfaltum
```
Correctly identifies Denis as the clear top reviewer (2x second place
score). All 6 CODEOWNERS shown as eligible.

**PR #4782** (13 files, by denik, bundle engine priority):
```
## Suggested reviewers
- @andrewnester -- recent work in `bundle/schema/`, `bundle/internal/schema/`, `cmd/bundle/generate/`
- @pietern -- recent work in `bundle/schema/`, `cmd/bundle/generate/`, `bundle/internal/schema/`
- @shreyas-goenka -- recent work in `bundle/schema/`, `bundle/internal/schema/`, `cmd/bundle/`
Confidence: medium

## Eligible reviewers
@anton-107, @simonfaltum
```
Suggests 3 reviewers when scores are close. Remaining CODEOWNERS shown
as eligible.

**PR #4785** (2 files, by MarioCadenas, apps bug fix):
```
## Suggested reviewers
- @arsenyinfo -- recent work in `cmd/apps/`
- @pietern -- recent work in `cmd/apps/`
- @pkosiec -- recent work in `cmd/apps/`
Confidence: low

## Eligible reviewers
@databricks/eng-apps-devex
```
Correctly suggests apps-area contributors (not the catch-all
CODEOWNERS). Shows the apps team as eligible. Low confidence since only
2 files.

**PR #4774** (28 files, by denik, direct engine grants):
```
## Suggested reviewers
- @andrewnester -- recent work in `bundle/direct/dresources/`, `acceptance/bundle/invariant/`
- @shreyas-goenka -- recent work in `bundle/direct/dresources/`
Confidence: high

## Eligible reviewers
@anton-107, @pietern, @simonfaltum
```
Correctly identifies the two main bundle/direct contributors. High
confidence with clear score separation.