feat(sdk): AI SDK custom useChat transport & chat.task harness #5449

Job	Run time
typecheck / typecheck	6m 42s
sdk-compat / Cloudflare Workers	2m 10s
sdk-compat / Bun Runtime	2m 7s
sdk-compat / Deno Runtime	2m 0s
e2e / 🧪 CLI v3 tests (windows-latest - pnpm)	3m 53s
sdk-compat / Node.js 22.12 (ubuntu-latest)	2m 5s
sdk-compat / Node.js 20.20 (ubuntu-latest)	2m 0s
e2e / 🧪 CLI v3 tests (ubuntu-latest - pnpm)	1m 57s
e2e / 🧪 CLI v3 tests (windows-latest - npm)	4m 6s
e2e / 🧪 CLI v3 tests (ubuntu-latest - npm)	1m 55s
units / packages / 🧪 Unit Tests: Packages (1, 1)	8m 56s
units / internal / 🧪 Unit Tests: Internal (2, 8)	4m 2s
units / internal / 🧪 Unit Tests: Internal (4, 8)	4m 3s
units / internal / 🧪 Unit Tests: Internal (1, 8)	3m 46s
units / internal / 🧪 Unit Tests: Internal (6, 8)	4m 2s
units / internal / 🧪 Unit Tests: Internal (5, 8)	4m 3s
units / internal / 🧪 Unit Tests: Internal (3, 8)	4m 1s
units / webapp / 🧪 Unit Tests: Webapp (8, 8)	6m 11s
units / webapp / 🧪 Unit Tests: Webapp (1, 8)	5m 54s
units / webapp / 🧪 Unit Tests: Webapp (7, 8)	2m 46s
units / webapp / 🧪 Unit Tests: Webapp (2, 8)	4m 47s
units / internal / 🧪 Unit Tests: Internal (8, 8)	2m 39s
units / webapp / 🧪 Unit Tests: Webapp (3, 8)	3m 56s
units / webapp / 🧪 Unit Tests: Webapp (4, 8)	6m 20s
units / webapp / 🧪 Unit Tests: Webapp (5, 8)	4m 33s
units / internal / 🧪 Unit Tests: Internal (7, 8)	4m 3s
units / webapp / 🧪 Unit Tests: Webapp (6, 8)	8m 25s
units / internal / 📊 Merge Reports	19s
units / webapp / 📊 Merge Reports	48s
units / packages / 📊 Merge Reports	21s
	1h 52m 50s

Provide feedback