Fix cache key collisions, HTTP scheme mixing, and Vary ambiguity

[aui]

Summary

This is a major release that overhauls cache key generation to fix correctness and HTTP alignment issues:

• Reduce wrong cache hits from digest collisions — cookie/header/device values now share one standard SHA-1 digest over a canonical string, instead of per-value truncated digests that could collide at scale.
• Stop http and https from sharing the same entry — URL scheme is included in default keys (RFC 9111 URI identity).
• Make Vary-aware keys unambiguous — explicit |v| / |vary| suffixes so base keys, Vary metadata, and variants cannot be parsed incorrectly.
• Keep keys debuggable without exposing secrets — fragment key names stay visible (#cookie:a|header:x-id@…); only normalized values are digested.
• Align cache lookup options with Workers Cache API — match() / delete() support ignoreMethod only; ignore query strings via cacheKeyRules.search: false, bypass Vary via sharedCache.ignoreVary.

Also includes compiled cache-key rules with a sync fast path, per-request header/cookie context sharing, tightened public exports, and expanded test coverage (~98.8% statements).

Breaking changes

• Existing cache entries miss until they expire or are revalidated.
• Default keys now include scheme (https://…); set scheme: false for the previous host-first shape.
• Remove cacheKeyPartDefiners / SharedCacheKeyPartDefiners; use built-in cacheKeyRules only.

Test plan

• pnpm test (331 tests, ~98.8% statement coverage)
• Verify cache hit/miss after deploy with new key format
• Confirm reverse-proxy setups using scheme: false if needed

[changeset-bot]

🦋 Changeset detected

Latest commit: f6926f4

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@web-widget/shared-cache	Major

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[codecov]

Codecov Report

❌ Patch coverage is 97.78024% with 20 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/cache-key.ts	97.59%	15 Missing and 3 partials ⚠️
src/cache.ts	97.26%	2 Missing ⚠️

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