# Collections Crate Review

Issue: #19
Branch: `feat/issue-19-collections-crate`
Date: 2026-06-10

## Scope

Add the first `0.2.0` workspace crate boundary:

- `crates/collections`
- root workspace registration
- root `collections` facade feature
- crate README and Rustdoc namespace documentation

## 7-Tier Review

### Tier 1 - Rust API Shape

PASS. The crate starts with namespace modules only and does not introduce fake
helper functions before the focused helper API issue (#20). The root facade
feature is optional and additive.

### Tier 2 - Workspace And Cargo Metadata

PASS. `crates/collections` is registered as a workspace member, has a focused
package name, uses workspace edition/rust-version/license/repository metadata,
and is wired through a workspace dependency.

### Tier 3 - Feature Flags

PASS. The root `collections` feature is optional and not included in default
features, preserving the narrow default facade.

### Tier 4 - Documentation

PASS. The crate README and crate/module Rustdoc explain the intended helper
namespaces and preserve the rule to prefer standard library APIs when they are
clear.

### Tier 5 - Behavior Risk

PASS. No collection helper behavior is claimed yet. The diff adds crate
structure and facade wiring only.

### Tier 6 - Validation

PASS.

- `git diff --check`
- `cargo fmt --all --check`
- `cargo check --workspace`
- `cargo test --workspace --all-features`
- `cargo clippy --workspace --all-targets --all-features -- -D warnings`
- `cargo doc --workspace --no-deps`
- `RUSTDOCFLAGS='-D warnings' cargo doc --workspace --no-deps`

### Tier 7 - Release/Milestone Fit

PASS. The change starts milestone `0.2.0` with a crate boundary only. Helper
APIs remain deferred to issue #20.

## Findings

No P0/P1/P2/P3 findings.

## Verdict

PASS.

P0 count: 0
P1 count: 0
