kvm2: domain and volume XML, metadata element and NoCloud seed builders

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

docs/plans-executions/2026-09-16-1333-kvm2-provider.md

@@ -5,7 +5,7 @@ Plan: [docs/plans/2026-09-16-1333-kvm2-provider.md](../plans/2026-09-16-1333-kvm
 - [x] Step 0 — Plan file and branch
 - [x] Step 1 — The spec, `docs/kvm2-provider-spec.md`
 - [x] Step 2 — Config wiring, IDs, state mapping, classify
-- [ ] Step 3 — Pure builders: domain and volume XML, metadata, seed
+- [x] Step 3 — Pure builders: domain and volume XML, metadata, seed
 - [ ] Step 4 — Transport, seam, decorator, fakes
 - [ ] Step 5 — Image cache and pool-space precheck
 - [ ] Step 6 — The four contract methods
@@ -56,7 +56,7 @@ re-derive the mapping.
 
 ## Step 2 — Config wiring, IDs, state mapping, classify
 
-2026-09-16 16:40. First subagent step. The brief named the allowed files,
+2026-09-16 16:38. First subagent step. The brief named the allowed files,
 the spec entries, the test names and the prohibition on
 `internal/provider/kvm/`; the agent reported nothing opened there, with one
 honest caveat: a `golangci-lint` run printed seven single source lines from
@@ -94,3 +94,34 @@ because the local toolchain is Go 1.27.0 while `go.mod` says 1.26 and the
 bundled staticcheck predates it; it reproduces on untouched packages, so lint
 is deferred to Step 10 with a toolchain note. The `.claude/settings.json`
 modification is still local and uncommitted.
+
+## Step 3 — Pure builders: domain and volume XML, metadata, seed
+
+2026-09-16 16:55. Second subagent step, new files only: `xml.go`,
+`metadata.go`, `volume.go`, `seed.go` and their tests (26 tests). The
+domain XML is built from `encoding/xml` structs, both disks are
+`type="file"` with resolved paths (the AppArmor lesson), UEFI is the default
+with the secure-boot feature disabled, the metadata element parses with or
+without its namespace declaration, and the seed ISO is staged under
+`os.TempDir()` (the library uses `os.MkdirTemp("", "")`, so `TMPDIR` is
+honoured; the test points it at a `t.TempDir()` and asserts nothing is left
+behind).
+
+Decisions the agent made, all accepted: `buildDomainXML` defaults an empty
+disk format to qcow2 and rejects anything but qcow2 or raw;
+`buildVolumeXML` rejects a non-positive capacity; `buildSeedISO` rejects an
+empty name; the guest-agent script still runs the enable-and-start step when
+the agent is already installed; the multipart boundary is random, so
+vendor-data is not byte-deterministic across calls (the seed is rebuilt every
+Create anyway).
+
+Commands:
+
+```sh
+gofmt -l ./internal/provider/kvm2 ; go vet ./internal/provider/kvm2/ && go test -race -count=1 ./internal/provider/kvm2/
+go build ./... && go test -short ./...
+```
+
+All `ok`. Review greps for a v1 import or v1 identifiers are empty; the only
+`type="volume"` in the package is the comment explaining why it is not used.
+The agent reported "files read outside the allowed set: none".