Complete portable request observability #118

Description

Track structured logging, automatic request timing, metrics hooks, distributed traces and logging destination configuration across adapters.

Main has log-level/endpoint configuration and a request logger that records elapsed time, but Cloudflare/Spin logger initialization is a no-op and no public metrics/tracing propagation API exists. KV operation timing logs are a separate delivered subset.

Steps to reproduce

1. Inspect logging configuration, request middleware and adapter logger initialization.
2. Compare delivered logging/timing with the remaining child acceptance scopes.

Expected behavior

Applications receive consistent, configurable operational evidence through portable APIs and documented provider integrations.

Impact

Operators cannot yet rely on a common request telemetry contract across all runtimes.

Proposed fix

Retain the existing logging and KV timing baseline, finish #119 and #121–123, and coordinate the generic timing collector in #446 / #389 with native diagnostics #397.

Done when

• Structured logging and automatic request timing have observable output on all supported adapters.
• Metrics hooks and distributed trace propagation are available without runtime coupling in core.
• Fastly and Cloudflare destination configuration is documented and implemented.
• Remaining children Provide consistent structured logs across adapters #119, Add request metrics hooks #121, Support distributed trace propagation #122 and Configure Fastly and Cloudflare logging destinations #123 are accepted; Expose request latency automatically #120 is recorded as delivered.

Related

• Children: Provide consistent structured logs across adapters #119, Expose request latency automatically #120, Add request metrics hooks #121, Support distributed trace propagation #122, Configure Fastly and Cloudflare logging destinations #123.
• Native diagnostics: Axum: add safe production diagnostics and trusted-proxy handling #397.
• Timing collector: Add a shared request-timing collector and opt-in attachment middleware #446.
• Built-in request logger
• Manifest logging schema
• Cloudflare logger initialization
• Spin logger initialization
• Related PR feat(core): add shared request timing collector and middleware #389; this PR alone does not establish completion of this issue.
• Related PR feat(axum): add safe diagnostics and trusted proxy metadata #409; this PR alone does not establish completion of this issue.