ci: reduce unit test flakiness and shard re-run cost #6880

Job	Run time
Detect changes	4s
packages / 🧪 Unit Tests: Packages (1, 1)	11m 43s
webapp / 🧪 Unit Tests: Webapp (3, 8)	3m 49s
webapp / 🧪 Unit Tests: Webapp (8, 8)	7m 19s
webapp / 🧪 Unit Tests: Webapp (7, 8)	9m 1s
webapp / 🧪 Unit Tests: Webapp (2, 8)	4m 58s
internal / 🧪 Unit Tests: Internal (1, 8)	6m 39s
webapp / 🧪 Unit Tests: Webapp (5, 8)	5m 36s
webapp / 🧪 Unit Tests: Webapp (1, 8)	6m 32s
typecheck / typecheck	6m 52s
e2e-webapp / 🧪 E2E Tests: Webapp	3m 11s
webapp / 🧪 Unit Tests: Webapp (4, 8)	7m 58s
internal / 🧪 Unit Tests: Internal (3, 8)	9m 8s
internal / 🧪 Unit Tests: Internal (5, 8)	6m 17s
internal / 🧪 Unit Tests: Internal (6, 8)	5m 24s
internal / 🧪 Unit Tests: Internal (2, 8)	12m 47s
internal / 🧪 Unit Tests: Internal (7, 8)	5m 45s
webapp / 🧪 Unit Tests: Webapp (6, 8)	3m 58s
internal / 🧪 Unit Tests: Internal (4, 8)	5m 42s
internal / 🧪 Unit Tests: Internal (8, 8)	6m 41s
sdk-compat	0s
e2e	0s
webapp / 📊 Merge Reports	47s
packages / 📊 Merge Reports	20s
internal / 📊 Merge Reports	19s
All PR Checks	3s
	2h 10m 53s

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