[clhodapp]

mkIntegration now builds lib.caisson.<integration>.types for every integration from its name and its class, as it builds mkModule from the class. No integration adds anything for it.

• types.module is the option type of a module of the class. It is the deferredModule type of nixpkgs, and it refuses a definition whose module states another class. A module states its class with _class. A module read from the registry states it in its key, modules.<class>.<name>@<project>. A function or a path states no class, and the type takes it unchecked.
• types.configuration takes what the mkConfiguration of the integration returns, or a deferred configuration. When the configuration is finalized, the type reads the type of its manifest and refuses a configuration of another integration. It forces nothing more of the manifest.
• An alt integration (nixos-minimal, home-manager-minimal) carries the types of its owner.

caisson.<integration>.configurations is now a lazy attribute set of that configuration type. A configuration of the wrong integration fails at the option, and the message names the option and the file of the definition:

error: `caisson.flake-parts.configurations.inner` in `/example/parent.nix`
is defined with a structural configuration, and the option takes a
flake-parts configuration. Declare it under `caisson.structural.configurations`.

The option types of the core module (libOverlay, pkgOverlay, libOverlays, pkgOverlays, manifest) move from lib.caisson.flake-parts.types to lib.caisson-core.types. The integrations overlay of caisson adds them to that namespace. caisson-core is written on builtins alone, and an option type is built on the library of nixpkgs, so caisson-core itself needs no change.

No repository in the workspace, topside or the site reads lib.caisson.flake-parts.types. The site documents it, and nix-caisson/nix-caisson.github.io gets its own PR.

Evaluation cost on ch-personal-machines, with every caisson pin of its lock overridden to caisson main and then to this branch (NIX_SHOW_STATS). Both evaluations produce the same drvPath.

	main	this branch
chris-desktop-2 toplevel, thunks	52,795,660	52,860,356
chris-desktop-2 toplevel, function calls	34,119,909	34,133,365
chris-desktop-2 toplevel, GC heap	3,355,705,344	3,355,705,344
chris@chris-desktop-2 home, thunks	42,246,728	42,311,424
chris@chris-desktop-2 home, function calls	27,254,465	27,267,921
chris@chris-desktop-2 home, GC heap	2,567,176,192	2,567,176,192
chris-desktop-2 toplevel, CPU seconds (two runs)	25.5, 28.1	32.6, 26.8
chris@chris-desktop-2 home, CPU seconds (two runs)	23.9, 25.5	27.7, 25.9

Each evaluation allocates about 65,000 more thunks, 0.12 % of the toplevel. The CPU times differ from run to run by more than they differ between the branches, on a machine with a load average near 6.

nix-caisson/topside#11 updates the topside goldens, which list the names of each namespace. nix-caisson/nix-caisson.github.io#93 updates the reference.

nix flake check passes locally, VM checks included.

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