feat(observability): instrument SWR fetch caches so cache metrics reach ClickHouse

[JonasJesus42]

Cache/upstream telemetry only reached ClickHouse for the edge and cachedLoader layers; the commerce apps' in-memory SWR fetch caches (VTEX today, and every Magento site) were dark, so we had no hit/miss ratio or upstream latency for the layer doing the real dedup/SWR work against provider APIs. This adds one shared, instrumented SWR cache — createFetchCache in @decocms/blocks/sdk/fetchCache, emitting deco.cache.requests{layer="swr",profile=<provider>} on HIT/STALE-HIT/MISS with provider-isolated Maps — and routes every commerce app through it plus the shared createInstrumentedFetch, so any current or future app is covered automatically (the vtex-swr layer is renamed to the provider-agnostic swr). VTEX's fetchCache becomes a thin binding over the shared util (no behavior change, now emits metrics); apps-magento gains setMagentoFetch/createMagentoFetch + magentoCachedFetch + an operation router; apps-salesforce gains createSalesforceFetch and defaults createHttpClient's fetcher to it so all loaders are instrumented without per-loader wiring. The contract is documented in CLAUDE.md and enforced by a guardrail test in apps-commerce that fails if a commerce app lacks an instrumented fetch. Verified: typecheck clean across the six affected packages and the full test suites pass (plus new fetchCache, magento instrumentation, and guardrail tests).

🤖 Generated with Claude Code

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Summary by cubic

Instrumented the shared SWR fetch cache and provider fetches so cache hit/miss and upstream latency metrics reach ClickHouse with clean labels. SWR now emits deco.cache.requests with layer="swr" and the backend in deco.cache.provider; VTEX, Magento, and Salesforce also emit http.client.request.duration.

• New Features

  • Added createFetchCache in @decocms/blocks/sdk/fetchCache emitting deco.cache.requests{layer="swr",provider=<backend>} on HIT/STALE-HIT/MISS.
  • Renamed cache layer label from vtex-swr to swr; SWR leaves deco.cache.profile unset and carries the backend in deco.cache.provider.
  • VTEX: routed through the shared cache; kept the same API (fetchWithCache, stats, clear).
  • Magento: added createMagentoFetch + setMagentoFetch, magentoCachedFetch, and an operation router to instrument all egress via one fetch.
  • Salesforce: added createSalesforceFetch; createHttpClient now defaults its fetcher to it so all loaders are covered.
  • Updated recordCacheMetric to accept a provider label; tests and docs reflect the new label scheme. Guardrail test ensures each commerce app ships an instrumentedFetch factory (factory existence only).

• Migration

  • Magento: call setMagentoFetch(createMagentoFetch()) at boot; use magentoCachedFetch for cacheable GETs.
  • Salesforce: no action needed; if you pass a custom fetcher to createHttpClient, wrap it with createSalesforceFetch({ baseFetch }).
  • Dashboards: filter deco.cache.layer="swr" and slice by deco.cache.provider (was vtex-swr and deco.cache.profile).

^{Written for commit 8d3f4db. Summary will update on new commits.}