fix(utils): classify validation errors strictly over network substring heuristics

[MsfPablo]

Summary

createErrorInfo misclassified validation errors as network errors when the message happened to contain a network-sounding substring like connection or fetch (#1136). The isNetworkError / isTimeoutError helpers match on loose .includes() substrings, so a message such as "validation failed for connection" was flagged as both a validation and a network error.

Validation now takes strict precedence over the network/timeout substring heuristics: when an error is a validation error, isNetworkError and isTimeoutError are forced to false. Real network errors (identified by error code such as ECONNREFUSED / ETIMEDOUT, or messages without a validation cue) are unaffected.

Behavior

message	before	after
validation failed for connection	validation + network	validation only
failed to fetch: connection refused	network	network
request failed + code: ETIMEDOUT	network + timeout	network + timeout

Testing

• Added two regression specs covering the overlapping-message case and a real network error without a validation cue.
• pnpm run test:types clean; error-formatter.spec.ts 28/28 in isolation; biome clean.
• Existing createErrorInfo network/timeout specs continue to pass.

Closes #1136.