feat(sdk): AI SDK custom useChat transport & chat.task harness #4968

Job	Run time
typecheck / typecheck	6m 32s
e2e / 🧪 CLI v3 tests (windows-latest - npm)	4m 1s
sdk-compat / Bun Runtime	2m 7s
e2e / 🧪 CLI v3 tests (ubuntu-latest - npm)	1m 46s
sdk-compat / Deno Runtime	2m 4s
e2e / 🧪 CLI v3 tests (windows-latest - pnpm)	3m 59s
sdk-compat / Node.js 22.12 (ubuntu-latest)	2m 1s
e2e / 🧪 CLI v3 tests (ubuntu-latest - pnpm)	1m 53s
sdk-compat / Cloudflare Workers	2m 18s
sdk-compat / Node.js 20.20 (ubuntu-latest)	2m 5s
units / packages / 🧪 Unit Tests: Packages (1, 1)	9m 30s
units / internal / 🧪 Unit Tests: Internal (1, 8)	5m 42s
units / internal / 🧪 Unit Tests: Internal (5, 8)	4m 4s
units / internal / 🧪 Unit Tests: Internal (3, 8)	10m 21s
units / internal / 🧪 Unit Tests: Internal (6, 8)	5m 45s
units / internal / 🧪 Unit Tests: Internal (7, 8)	5m 41s
units / internal / 🧪 Unit Tests: Internal (8, 8)	6m 17s
units / webapp / 🧪 Unit Tests: Webapp (3, 8)	6m 14s
units / webapp / 🧪 Unit Tests: Webapp (2, 8)	4m 23s
units / internal / 🧪 Unit Tests: Internal (2, 8)	10m 19s
units / webapp / 🧪 Unit Tests: Webapp (5, 8)	8m 0s
units / webapp / 🧪 Unit Tests: Webapp (6, 8)	2m 44s
units / webapp / 🧪 Unit Tests: Webapp (1, 8)	5m 53s
units / webapp / 🧪 Unit Tests: Webapp (7, 8)	6m 7s
units / webapp / 🧪 Unit Tests: Webapp (8, 8)	2m 47s
units / internal / 🧪 Unit Tests: Internal (4, 8)	6m 1s
units / webapp / 🧪 Unit Tests: Webapp (4, 8)	3m 59s
units / webapp / 📊 Merge Reports	41s
units / packages / 📊 Merge Reports	20s
units / internal / 📊 Merge Reports	24s
	2h 13m 58s

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