perf: optimize Echo dispatch and add reproducible benchmarks

[cmilesio]

What

• Replace per-request Echo adapter allocation with a zero-allocation native context view, dispatch Web routes from Echo's resolved route, and compile middleware chains once while preserving late root middleware registration.
• Rework timeout handling around detached request ownership and a buffered response so completion, expiry, cancellation, and panic have one authoritative winner.
• Run WebSocket middleware before upgrade so middleware can reject a handshake before 101 Switching Protocols.
• Add a reproducible comparison with net/http, Echo, Gin, Chi, Gorilla Mux, and httprouter, including raw samples, a deterministic SVG, methodology, source provenance, and CI verification.

Why

The Echo path had avoidable adapter allocations and middleware reconstruction on hot requests, while timeout work could outlive ownership of a pooled request context. Fixing those issues restores competitive performance and makes cancellation behavior deterministic.

The benchmark records seven rotated single-core samples with environment and dependency metadata. CI verifies source currentness and deterministic rendering instead of comparing machine-dependent performance or enforcing rankings.

Compatibility

Source/API, configuration, persisted-data, and minimum-Go-version compatibility are preserved. Runtime behavior changes intentionally: middleware constructors run once at registration, WebSocket middleware can reject before upgrade, and state crossing a timeout boundary must use web.Context.Set/Get rather than the native Echo store.

Validation

• Root, docs, and examples tests and vet pass, including GOWORK=off nested-module validation.
• Root and docs race suites and strict checkptr validation pass.
• Module files are tidy, README generation is idempotent, and make benchmark-svg-verify passes twice with identical artifact hashes.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.38744% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
adapter/echoweb/context.go	98.86%	0 Missing and 3 partials ⚠️
adapter/echoweb/router.go	99.51%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!