Add docs for Workers Caching — caching HTTP responses from a Worker
so that Cloudflare serves them without executing the Worker.

New pages under src/content/docs/workers/cache/:

- configuration.mdx — enabling caching, Cache-Control semantics,
  TTL and stale-while-revalidate guidance, cf-cache-status, Cache-Tag
- cache-keys.mdx — what the cache key includes, multi-tenant safety
  with ctx.props, invalidating cache across deployments
- purge.mdx — ctx.cache.purge() with tags, pathPrefixes, and
  purgeEverything; versioned purging with the version metadata binding
- debugging.mdx — diagnosing why caching is not behaving as expected
- limitations.mdx — unsupported scenarios, limits, relationship to
  zone cache, the Cache API, and fetch() subrequests

index.mdx as a landing page with a quickstart showing wrangler deploy +
curl observing HIT/MISS, plus a Durable Object wrapping pattern for
caching DO responses.

workers/platform/pricing.mdx gets a worked example showing CPU savings
with an 80% cache hit rate.

* [Workers] Correct and expand Workers Caching docs

Round of corrections and additions based on review against pingora-origin
and edgeworker cache-handler source.

Corrections:

- Responses with no Cache-Control are cached by default via RFC 9111
  heuristic freshness; the docs previously said the opposite. Add a
  table of the 10 default-cacheable status codes and their TTLs.
- s-maxage, must-revalidate, and proxy-revalidate disable both
  stale-while-revalidate and stale-if-error, not just s-maxage with SWR.
- no-cache caches with zero freshness rather than bypassing. Document
  the EXPIRED, REVALIDATED, and UPDATING outcomes precisely.
- x-forwarded-scheme rule was reworded incorrectly; restored.

Additions:

- Request collapsing section with the 20s cache lock.
- stale-if-error section, including the default (infinite) and the
  carve-out for s-maxage / must-revalidate / proxy-revalidate.
- 520-526 and 206 are never cached, even with explicit Cache-Control.
- Cache Deception Armor activation conditions for the heuristic-
  freshness path.
- GET and HEAD share a single cache entry; HEAD on a cold cache is
  converted to GET internally.
- Custom RPC methods and WebSocket upgrades bypass the cache.
- Cloudflare-Workers-Version-Key request header is part of the cache key.
- Cache-Tag character set (printable ASCII), 1024 chars per tag,
  1000 tags per response, case-insensitive purge matching, silent
  drop of invalid tags.
- Standardized the Cf-Cache-Status value list across files.
- tags and pathPrefixes can be combined in a single purge() call.
- Cf-Cache-Status: STALE debugging section.

* [Workers] Style fixes from docs bot review

Address style guide warnings from the cloudflare-docs-bot review on
PR #31149:

- Replace directional words ('table below', 'listed above') with
  direct references.
- Replace 'doesn't' with 'does not'.
- Replace 'see [link]' with 'refer to [link]' in newly added text.
- Remove 'Note that' filler.
- Break a semicolon-joined sentence into two.