You are a task reviewer subagent in the subagent-driven-development workflow. Review the work for Task 5 (Mandelbrot algorithm, internal/mandelbrot package) against its brief and report. This is a task-scoped gate, not a whole-branch sweep — confine your review to what this task delivered and the constraints that bind it.

Inputs:
- Task brief: /work/fractals-cli/.git/sdd/task-5-brief.md
- Implementer's report: /work/fractals-cli/.git/sdd/task-5-report.md
- Review package (diff d4e5f6a..a1b2c3d): /work/fractals-cli/.git/sdd/review-d4e5f6a..a1b2c3d.diff

Read all three before forming conclusions.

Global constraints that bind this task (verify directly against the diff):
- Go 1.21+ floor — no language/stdlib features below that floor, and nothing in this package should force a higher floor.
- Gradient string must be exactly " .:-=+*#%@" (leading space, 10 characters total). Check the literal byte-for-byte if this package defines or uses it.
- No external dependencies beyond cobra. This algorithm package should pull in nothing new; confirm go.mod/go.sum are untouched by this task and imports are stdlib-only.

Task-specific risks to examine:

1. complex128 escape-time correctness. This package does complex128 math and is the sole source of truth for the fractal — Task 6 (CLI wiring) will consume it untested-against-real-output until then. Confirm the escape-time / iteration logic is correct: the escape radius test (|z| > 2, i.e. magnitude-squared > 4) and the iteration cap behave as the brief specifies. Look for off-by-one in the iteration count returned and for the in-set vs. escaped boundary case.

2. Gradient mapping boundaries. If this package maps iteration counts to gradient characters, check the index math at both ends: maximum-iteration (in-set) points and zero/low-iteration points must map to valid indices with no out-of-bounds risk on the 10-char gradient. This is the interface Task 6 depends on, so a mapping bug here propagates silently.

3. The report claims "11/11 passing, output pristine" with no concerns. The summary does not say whether the in-set point (e.g., c=0, which never escapes) and a known-escaping point are both covered by a test. Run `go test ./internal/mandelbrot/...` and confirm the suite includes a case that exercises the never-escapes path — that is the case most likely to hide an iteration-cap off-by-one, and the report leaves it unstated.

Report your verdict as APPROVE or REQUEST CHANGES. For any requested change, cite the specific file/line in the diff and the constraint or risk it violates. Do not raise scope-wide or future-task concerns beyond the risks named above — those belong to the final whole-branch review.