fix(core): drop api_format from Azure targets; surface pi-ai errors

[christso]

Summary

Two regressions from the Vercel AI SDK → pi-ai migration (#1206) broke Azure evals end-to-end whenever a target had api_format: chat (or unset, on a config still defaulting to it):

1. API version mismatch. The migration kept the api_format field but pi-ai's azure-openai-responses provider always hits /openai/v1/responses. With chat-style defaults still in place, AgentV sent ?api-version=2024-12-01-preview to the Responses path → Azure rejected with 400 "API version not supported" on every call.
2. Silent error swallowing. invokePiAi never inspected pi-ai's stopReason. When pi-ai surfaced the 400 as { stopReason: 'error', errorMessage: '...', content: [] }, the adapter happily returned an empty assistant message → graders reported misleading "Unexpected EOF" JSON parse failures, completely hiding the underlying HTTP error.

Fix

• Remove api_format from Azure targets entirely. Pi-ai's adapter only exposes the Responses path, so a chat/responses switch on this provider has no effect. Default Azure api version to v1 (matching /openai/v1/responses). Reject api_format on Azure targets at both validation and resolution time with a migration message pointing at provider: openai for chat-completions-only deployments. api_format remains supported on provider: openai.
• Throw from invokePiAi when pi-ai returns stopReason: 'error'. The thrown message includes the parsed HTTP status so isRetryableError can decide retry behavior correctly.
• Drop api_format from the repo's .agentv/targets.yaml and update the Azure provider docs with the migration path.

There's also a small follow-up commit doing pure biome format --write on apps/cli/src/self-update.ts and apps/cli/test/self-update.test.ts — pre-existing lint failures from #1213 that were blocking the pre-push hook.

Test plan

• All 1752 core unit tests pass
• All 502 CLI unit tests pass
• Validator and resolver tests updated; both surface the migration error for api_format on Azure
• Red UAT (main): agentv eval examples/features/basic/evals/dataset.eval.yaml --target default with AZURE_OPENAI_API_FORMAT=chat (or unset) → 7/7 tests fail; agent + grader return empty content; surface error: LLM grader "llm-grader" failed after 3 attempts (... Unexpected EOF) — skipped. Captured in conversation; pi-ai's actual response is 400 API version not supported.
• Green UAT (this branch): Same eval, same .env, with the updated .agentv/targets.yaml → code-review-javascript: 98% PASS in 6.3s.
• Migration error UAT: agentv validate on a targets file containing api_format: chat for an azure target → emits [targets[0].api_format] The 'api_format' field is no longer supported on Azure targets. ... use 'provider: openai' with a deployment-scoped 'base_url' instead. agentv eval against the same targets file refuses to start with the same error.
• Silent-error fix UAT: Force AZURE_OPENAI_API_VERSION=bogus-version → eval surfaces ERROR: pi-ai call failed: HTTP 400 API version not supported (clear) instead of "Unexpected EOF" (misleading).

🤖 Generated with Claude Code

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