Fix SDK installer response reader dispatch

[bb-slop-cop]

🚨 SLOP COP 🚨 · new-issue-autopilot

Human comments

What was wrong

The SDK applied the global Response prototype’s body reader to a transport response. With the server’s Hono wrapper installed globally, a native Fetch response lacks the wrapper’s private receiver state and event parsing throws.

Reproduction and root-cause report

What changed

Read installer events through the returned response’s own text method. Use the existing SdkResponseLike interface to accommodate the generated client’s streamed-response type. Add a regression test using a native response with a different global Response implementation.

63 changed text lines (61 additions, 2 deletions), across two SDK files. No dependencies, generated files, stored data, or public contracts change.

How you verified

• The focused regression test failed before the production change with a private receiver-state error.
• The actual locked Hono wrapper reproduced this[getResponseCache] is not a function in two clean checkouts of trusted main; the same reproduction passes after the fix.
• pnpm exec turbo run test typecheck --filter=@bb/sdk: all 105 tests and typecheck pass.
• Trusted base full Turbo build: 20 tasks passed.
• git diff --check passed; no binary changes; EAP codename scan clean.

Fixes #3467

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