fix(ai): support JSONL responses in Google-compatible streams

[Loxia106]

What

• Select newline-delimited JSON parsing for explicit NDJSON and JSONL response media types.
• Preserve SSE parsing and event callbacks for standard, missing, and unknown media types.
• Add focused coverage for media-type normalization, unknown-type fallback, unterminated final records, malformed input, usage, finish state, and callback behavior.
• Document the compatibility fix in the AI package changelog.

Why

Google-compatible streaming providers can return newline-delimited JSON while exposing the same streaming response schema. Treating those records as SSE drops valid chunks because they do not use SSE framing.

The parser selection is limited to an explicit media-type allowlist so unknown response types continue to use the existing SSE path.

Testing

• bun test packages/ai/test/google-stream-content-type.test.ts packages/ai/test/google-safety-stop.test.ts — 12 passed, 0 failed, 93 assertions
• bun --cwd=packages/ai run check — passed
• git diff --check upstream/dev...HEAD — passed
• CI=0 bun check — blocked by an unchanged upstream canonicalization self-test (expected exit 1, got 0); the focused tests and complete AI package check pass

GJC verdict

gajae.pr-review-verdict.v1 merge-approved sha256:ad54358911b14111ac42147464e0baf1c0569a119a44d32d28e42c6901475b03 reviewer:architect evidence:local-command:bun-test+packages-ai-check

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• Target branch is dev
• bun check passes
• Tested locally
• CHANGELOG updated (if user-facing)
• Verdict above matches the exact PR head, not an earlier commit