[adamtheturtle]

Upgrade Pyrefly to 1.4.0 and initialize status, body, and headers in both validator-error base constructors. All 47 concrete error classes now supply complete response data to their base constructor, removing the uninitialized-field suppressions. Existing HTTP response tests exercise the constructors through concrete errors; no new tests or test jobs are added.

Depends on #3781 for the CI credential repair. This PR targets its branch so the credential changes stay in that prerequisite.

Validation:

• 44 existing date-header response tests passed; 22 live-backend cases were skipped.
• Pre-commit and full pre-push checks passed, including the test partition check, workflow lint, and type checks.
• No new type-checker suppressions or casts.