`platform.*` diagnostics

Owner: the platform spec (defs/platform.ts). The status is the code's own; the exit comes from its category (CATEGORIES). A warning or info code never sets the status or the exit.

Code	Category	Severity	Status	Exit	Retry	Fix	Args
`platform.cpu_exceeded`	platform	error	503	1	no	—	`op`
`platform.internal`	platform	error	500	1	no	—	`trace`
`platform.overloaded`	platform	error	503	1	no	—	—
`platform.timeout`	temporary	error	504	1	backoff	—	`wall_ms`
`platform.unavailable`	temporary	error	503	1	backoff	—	`retry_after_ms`

platform.* diagnostics

`platform.*` diagnostics