feat(sdk): AI SDK custom useChat transport & chat.task harness #5284

Job	Run time
sdk-compat / Node.js 22.12 (ubuntu-latest)	3m 28s
sdk-compat / Bun Runtime	2m 35s
sdk-compat / Deno Runtime	2m 34s
e2e / 🧪 CLI v3 tests (ubuntu-latest - npm)	1m 55s
sdk-compat / Node.js 20.20 (ubuntu-latest)	2m 44s
units / packages / 🧪 Unit Tests: Packages (1, 1)	9m 18s
e2e / 🧪 CLI v3 tests (windows-latest - npm)	3m 25s
typecheck / typecheck	6m 53s
sdk-compat / Cloudflare Workers	2m 34s
e2e / 🧪 CLI v3 tests (ubuntu-latest - pnpm)	1m 58s
e2e / 🧪 CLI v3 tests (windows-latest - pnpm)	4m 9s
units / internal / 🧪 Unit Tests: Internal (2, 8)	4m 42s
units / internal / 🧪 Unit Tests: Internal (3, 8)	4m 45s
units / internal / 🧪 Unit Tests: Internal (1, 8)	4m 28s
units / internal / 🧪 Unit Tests: Internal (8, 8)	3m 2s
units / internal / 🧪 Unit Tests: Internal (5, 8)	4m 46s
units / webapp / 🧪 Unit Tests: Webapp (6, 8)	4m 0s
units / internal / 🧪 Unit Tests: Internal (4, 8)	4m 52s
units / webapp / 🧪 Unit Tests: Webapp (5, 8)	4m 2s
units / webapp / 🧪 Unit Tests: Webapp (2, 8)	4m 1s
units / internal / 🧪 Unit Tests: Internal (7, 8)	4m 46s
units / webapp / 🧪 Unit Tests: Webapp (1, 8)	4m 4s
units / webapp / 🧪 Unit Tests: Webapp (8, 8)	3m 2s
units / webapp / 🧪 Unit Tests: Webapp (3, 8)	3m 44s
units / internal / 🧪 Unit Tests: Internal (6, 8)	4m 44s
units / webapp / 🧪 Unit Tests: Webapp (4, 8)	4m 0s
units / webapp / 🧪 Unit Tests: Webapp (7, 8)	4m 2s
units / webapp / 📊 Merge Reports	26s
units / internal / 📊 Merge Reports	24s
units / packages / 📊 Merge Reports	23s
	1h 49m 46s

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