chore: release hardening — non_exhaustive, missing_docs, cargo-deny, gitignore

[27Bslash6]

Summary

• Add #[non_exhaustive] to CachekitError and BackendErrorKind for semver safety
• Enable #![warn(missing_docs)] and document all public items
• Fix deny.toml schema for cargo-deny 0.19.x
• Add MPL-2.0, BSL-1.0, CDLA-Permissive-2.0 to license allowlist
• Update rustls-webpki 0.103.9 → 0.103.13 (RUSTSEC-2026-0049/0098/0099/0104)
• Untrack CLAUDE.md, gitignore all AI agent configs

Test plan

• cargo test --features "cachekitio,redis,encryption,l1,macros" — 105 tests passing
• cargo clippy -- -D warnings — clean
• cargo deny check — advisories ok, bans ok, licenses ok, sources ok
• cargo fmt --check — clean
• Verify #[non_exhaustive] on CachekitError and BackendErrorKind
• Verify #![warn(missing_docs)] enabled in lib.rs

Summary by CodeRabbit

Release Notes

• New Features

  • Added L1 cache metrics exposure including hit/miss counters and cache performance statistics.
  • Introduced response headers for cache metrics with hit-rate calculations.

• Documentation

  • Expanded documentation across library modules for improved API clarity and configuration guidance.

• Chores

  • Updated dependency policies and configuration management settings.

[coderabbitai]

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Free

Run ID: 44391e8d-ed65-444a-b688-5ff0234ed51f

📥 Commits

Reviewing files that changed from the base of the PR and between 6794911 and b67cddd.

⛔ Files ignored due to path filters (1)

• Cargo.lock is excluded by !**/*.lock

📒 Files selected for processing (10)

• .gitignore
• CLAUDE.md
• crates/cachekit/src/backend/mod.rs
• crates/cachekit/src/error.rs
• crates/cachekit/src/key.rs
• crates/cachekit/src/l1/mod.rs
• crates/cachekit/src/lib.rs
• crates/cachekit/src/metrics.rs
• crates/cachekit/src/url_validator.rs
• deny.toml

💤 Files with no reviewable changes (1)

• CLAUDE.md

---

📝 Walkthrough

Walkthrough

This pull request adds comprehensive module and item documentation across the cachekit library, introduces breaking changes via #[non_exhaustive] attributes on error types, adds new metrics API surface (L1Stats, MetricsProvider), updates cargo-deny configuration with new allowed licenses, removes AI documentation (CLAUDE.md), and updates .gitignore patterns.

Changes

Cohort / File(s)	Summary
Documentation & Linting crates/cachekit/src/lib.rs, crates/cachekit/src/backend/mod.rs, crates/cachekit/src/key.rs, crates/cachekit/src/l1/mod.rs, crates/cachekit/src/url_validator.rs	Adds crate-level #![warn(missing_docs)] lint and rustdoc comments for modules, types, and public functions to improve API documentation coverage.
Breaking API Changes crates/cachekit/src/error.rs	Adds #[non_exhaustive] attributes to CachekitError and BackendErrorKind enums; reformats PayloadTooLarge variant to multi-line struct-style with documented fields.
New Metrics API crates/cachekit/src/metrics.rs	Introduces L1Stats struct and MetricsProvider type alias alongside documentation for metrics_headers function to expose cache hit/miss statistics and computed hit-rate headers.
Configuration & Ignore deny.toml, .gitignore	Updates cargo-deny policy with new allowed licenses (BSL-1.0, CDLA-Permissive-2.0, MPL-2.0) and workspace-scoped unmaintained handling; adds .gitignore patterns for AI agent configuration files.
Documentation Removal CLAUDE.md	Deletes entire file containing Rust SDK structure, features, quick-start, build examples, and environment variable documentation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Docs now flourish, bright and clear,
Non-exhaustive types appear!
Metrics bloom with stats so fine,
L1 hits and misses align,
A polished library for all to cheer! ✨

---

Note

🎁 Summarized by CodeRabbit Free

Your organization is on the Free plan. CodeRabbit will generate a high-level summary and a walkthrough for each pull request. For a comprehensive line-by-line review, please upgrade your subscription to CodeRabbit Pro by visiting https://app.coderabbit.ai/login.

_{Comment @coderabbitai help to get the list of available commands and usage tips.}