feat(sdk): AI SDK custom useChat transport & chat.task harness #5443

Job	Run time
typecheck / typecheck	5m 58s
sdk-compat / Node.js 22.12 (ubuntu-latest)	1m 54s
sdk-compat / Node.js 20.20 (ubuntu-latest)	2m 5s
sdk-compat / Cloudflare Workers	2m 22s
sdk-compat / Deno Runtime	2m 13s
sdk-compat / Bun Runtime	2m 9s
e2e / 🧪 CLI v3 tests (windows-latest - pnpm)	4m 6s
e2e / 🧪 CLI v3 tests (windows-latest - npm)	4m 15s
e2e / 🧪 CLI v3 tests (ubuntu-latest - npm)	1m 56s
e2e / 🧪 CLI v3 tests (ubuntu-latest - pnpm)	1m 55s
units / packages / 🧪 Unit Tests: Packages (1, 1)	6m 11s
units / internal / 🧪 Unit Tests: Internal (3, 8)	3m 42s
units / webapp / 🧪 Unit Tests: Webapp (5, 8)	4m 38s
units / webapp / 🧪 Unit Tests: Webapp (6, 8)	6m 11s
units / webapp / 🧪 Unit Tests: Webapp (4, 8)	6m 12s
units / webapp / 🧪 Unit Tests: Webapp (8, 8)	6m 2s
units / webapp / 🧪 Unit Tests: Webapp (7, 8)	2m 54s
units / webapp / 🧪 Unit Tests: Webapp (2, 8)	4m 7s
units / webapp / 🧪 Unit Tests: Webapp (1, 8)	5m 57s
units / internal / 🧪 Unit Tests: Internal (1, 8)	3m 26s
units / internal / 🧪 Unit Tests: Internal (2, 8)	3m 41s
units / internal / 🧪 Unit Tests: Internal (4, 8)	3m 44s
units / internal / 🧪 Unit Tests: Internal (6, 8)	3m 42s
units / internal / 🧪 Unit Tests: Internal (8, 8)	2m 43s
units / internal / 🧪 Unit Tests: Internal (5, 8)	3m 42s
units / internal / 🧪 Unit Tests: Internal (7, 8)	3m 42s
units / webapp / 🧪 Unit Tests: Webapp (3, 8)	3m 12s
units / internal / 📊 Merge Reports	25s
units / packages / 📊 Merge Reports	1s
units / webapp / 📊 Merge Reports	1s
	1h 43m 6s

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