Seats are a closed set, a seat's holder answers for what it delivers, and a build source may live on the git seat

Implements novox/hq ADR 0110 and 0111.

The seat set lives in internal/catalogue/seats.go: fourteen seats, each with a scope, what occupying
it delivers, and the record that made it one. A test asserts the count and a decision per entry, so
changing the set means finding the argument, as the host's vocabulary test does. The first set is
every seat already claimed — including the-private-network, which the network module claims from a
manifest composed in this repository's code, not from any module.json — plus npm-package-registry
(ADR 0109) and git (ADR 0111). A test parses every catalogue manifest and this repository's own and
fails on any refused claim, so closing the set refuses nothing in use.

ParseManifest now refuses a claim on a seat the mesh does not define, a seat claimed at another
scope, and a delivering seat claimed by a module that does not provide what it delivers. A
malformed claim is refused once, for being malformed.

Resolution: among several providers of a mesh provision, a pin still wins; then the holder of the
seat that delivers it; then the only provider; otherwise refused as before. ADR 0009's "never
guessed" holds — the seat is the choice made once, mesh-wide, rather than a pin per consumer node.
A provider now carries the module it came from, because a provider is a (node, module) pair and the
pair is what tells a holder from a neighbour on the same machine.

The planner's second pass is now given the first pass's holdings. Without them, a node consuming a
seat-delivered provision was refused there, and a refused node's own claims dropped out of what the
mesh holds — letting a second holder of one of its seats pass unrefused.

`seats [--json]` lists every seat, what it delivers, and each holder, derived from assignments
every time and never stored. Unheld seats are listed. A stored claim outside the set — possible
for a manifest registered before the set closed, since stored manifests are not re-validated — is
shown rather than hidden.

`build --self <owner>/<repo>` builds from a repository on the git seat's holder. The clone URL is
composed at build time from the holder's node and what it serves for git; the recorded source is the
path and the seat (migration 0032), never an address, so a moved forge changes nothing recorded.
Nobody holding the seat refuses self-hosted builds and says so; external URLs are unchanged. An
address passed with --self is refused rather than recorded as a path.

Replaces three foundation tests that defended the builder's carried package binding. The catalogue
removed that binding when the builder began requiring the registry through a real grant, so the
tests were already failing on main; they now assert the builder requires what the npm seat delivers
and carries no copy of its own, and that the forge holds the npm and git seats.

Verified: go vet clean; the whole suite passes against a throwaway Postgres (make postgres), the new
inventory tests included; gofmt clean apart from cmd/mesh-builder/stdout_test.go, which fails on
main too.

cmd/mesh-controller/main.go

@@ -114,6 +114,8 @@ func run() error {
 		return planCommand(ctx, args[1:])
 	case "push":
 		return pushCommand(ctx, args[1:])
+	case "seats":
+		return seatsCommand(ctx, args[1:])
 	case "status":
 		return statusCommand(ctx, args[1:])
 	case "version":
@@ -157,6 +159,7 @@ func usage() {
   upgrade <name> roll-out [--together]   ...send it to the machines running it
   upgrade <name> record          ...record that they are behind, and send nothing
   status [--json]                what is wrong, what is quiet, and what is out of date
+  seats [--json]                 every seat this mesh defines, what it delivers, and who holds it
   board [--listen ADDR]          the same three questions, as a page that holds nothing
   api --issuer URL [--listen A]  assign and unassign over http, for a surface that is not here
   assign <node> <module>         put a module on a node