Entire

I’ll rename the diagnostics model-family packages (gyrokinetics→gk, vlasov→vm, moments→mom, with pkpm unchanged), then update imports, discovery wiring, tests, and architecture references so the enforced layer map stays accurate.

The package names also drive public import paths and the gyrokinetic CLI namespace. I’m treating the requested abbreviations as canonical Python package names—diagnostics.gk, .vm, .mom, .pkpm—while leaving the separate operations.gyrokinetics package unchanged.

The canonical imports and docs now use the abbreviated packages, and the public gyrokinetic facade is pg.gk. I’ve also updated generated-command expectations from gyrokinetics-* to gk-*; next I’m running the focused diagnostics and architecture tests to catch any import-path residue.

The focused suite passed (265 passed, 1 skipped). The full suite is through 93% with no failures; one of the existing late tests is taking longer, so I’m letting it finish before doing the final diff audit.

Renamed diagnostics packages to:

gyrokinetics → gk
vlasov → vm
moments → mom
pkpm unchanged

Updated imports, pg.gk, CLI names (gk-*), tests, examples, and architecture docs.

Verification: 416 passed, 4 skipped.