fix(module): run scripts/fetch-upstream-manifests (#84)

Closes #83. Part of #54; implements #63 Decision 5 ("Coordinated rename flip").

## What changed

One string literal in `internal/app/app.go:388`:

```go
[]string{"scripts", "fetch-hak-manifest"} -> []string{"scripts", "fetch-upstream-manifests"}
```

sow-module renamed its half in ShadowsOverWestgate/sow-module#57
(`scripts/fetch-hak-manifest.sh` -> `scripts/fetch-upstream-manifests.sh`,
extended to resolve the topdata channel as well). The script name is a
hardcoded path convention shared by the two repos, not config, so both sides
only work when they carry the same name.

No doc in this repo named the old script (`grep` over the tree found the one
call site only), so nothing else needed touching.

## No fallback, by decision

Per #63 Decision 5: no transitional symlink, no Go-side fallback. Both sides
flip and the short broken window is accepted, because the failure is loud and
unmistakable (`required project script is missing`). A fallback would keep
both names alive forever.

## Merge order matters

`sow-module/.gitea/workflows/release.yml` runs `nix flake update sow-tools`, so
it always builds against the latest crucible, unpinned. Every crucible module
build in sow-module fails between sow-module#57 merging and a crucible release
carrying this flip. **Merge sow-module#57 and cut a crucible release back to
back** to keep that gap short.

## Checks

- `go build ./...`, `go vet ./internal/app/`, and the full `go test ./...` suite pass.
- No test covers this call path, and none was added: it is a single hardcoded
  constant that has to match the other repo, so a test here could only assert
  the literal against itself. The real check is the sow-module build.

## Still open on the issue's "done when"

- [x] app.go runs `scripts/fetch-upstream-manifests`
- [x] no doc in this repo names `fetch-hak-manifest`
- [ ] a crucible release is cut, and the crucible module build succeeds in a
      sow-module checkout at #57's head — needs a release after this merges

🤖 Generated with [Claude Code](https://claude.com/claude-code)Reviewed-on: #84
Reviewed-by: xtul <mpiasecki720@protonmail.com>
Co-authored-by: vickydotbat <vickydotbat@tutamail.com>

internal/app/app.go

@@ -385,7 +385,7 @@ func refreshBuildModuleManifest(ctx context, p *project.Project, progress func(s
 	}
 
 	progress("Refreshing hak list from the latest published sow-assets manifest...")
-	if err := runProjectScript(ctx, p, []string{"scripts", "fetch-hak-manifest"}, manifestPath); err != nil {
+	if err := runProjectScript(ctx, p, []string{"scripts", "fetch-upstream-manifests"}, manifestPath); err != nil {
 		return "", "", err
 	}
 	if _, err := pipeline.ApplyHAKManifest(p, manifestPath); err != nil {