feat(sdk): AI SDK custom useChat transport & chat.task harness #5198

Job	Run time
sdk-compat / Bun Runtime	55s
typecheck / typecheck	1m 6s
sdk-compat / Node.js 20.20 (ubuntu-latest)	1m 6s
sdk-compat / Cloudflare Workers	53s
sdk-compat / Deno Runtime	48s
e2e / 🧪 CLI v3 tests (ubuntu-latest - pnpm)	52s
sdk-compat / Node.js 22.12 (ubuntu-latest)	41s
e2e / 🧪 CLI v3 tests (ubuntu-latest - npm)	1m 6s
units / packages / 🧪 Unit Tests: Packages (1, 1)	1m 7s
e2e / 🧪 CLI v3 tests (windows-latest - npm)	58s
e2e / 🧪 CLI v3 tests (windows-latest - pnpm)	1m 0s
units / internal / 🧪 Unit Tests: Internal (5, 8)	1m 8s
units / internal / 🧪 Unit Tests: Internal (2, 8)	42s
units / internal / 🧪 Unit Tests: Internal (6, 8)	54s
units / internal / 🧪 Unit Tests: Internal (4, 8)	1m 8s
units / internal / 🧪 Unit Tests: Internal (3, 8)	1m 3s
units / webapp / 🧪 Unit Tests: Webapp (5, 8)	48s
units / internal / 🧪 Unit Tests: Internal (1, 8)	1m 6s
units / webapp / 🧪 Unit Tests: Webapp (1, 8)	1m 9s
units / internal / 🧪 Unit Tests: Internal (7, 8)	1m 6s
units / webapp / 🧪 Unit Tests: Webapp (2, 8)	1m 7s
units / internal / 🧪 Unit Tests: Internal (8, 8)	1m 8s
units / webapp / 🧪 Unit Tests: Webapp (7, 8)	1m 7s
units / webapp / 🧪 Unit Tests: Webapp (6, 8)	51s
units / webapp / 🧪 Unit Tests: Webapp (4, 8)	1m 6s
units / webapp / 🧪 Unit Tests: Webapp (8, 8)	42s
units / webapp / 🧪 Unit Tests: Webapp (3, 8)	1m 6s
units / packages / 📊 Merge Reports	1s
units / webapp / 📊 Merge Reports	1s
units / internal / 📊 Merge Reports	1s
	26m 46s

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