Emit declared build parameters into build-graph.json

**Problem**

`build-graph.json` (the editor-tooling contract in `BuildGraphUtility`) carries only targets. The build's `[Parameter]`/`[Secret]` members — e.g. `NuGetApiKey` on `IPublish`, the set `dotnet fallout --help` lists — never reach the VS Code extension, so it can't surface them.

**Outcome**

Additive `parameters[]` in `build-graph.json`, projected from the build's declared parameters. Schema stays **v1** (new field is backward-compatible):

```jsonc
{ "name": "NuGetApiKey", "secret": true, "description": "…", "declaredIn": "IPublish" }
```

**Acceptance criteria**

- All declared `[Parameter]` members are projected, **including inherited component params** (IPublish, etc.) — matching `--help`'s set.
- `[Secret]` members flagged `secret: true`.
- Fields: `name`, `secret`, `description`, `declaredIn`.
- `SchemaVersion` unchanged (additive); existing consumers unaffected.
- `BuildGraphUtilitySpecs` updated to cover the projection.

Context: [ADR-0009] run-config discussion; feeds the extension issue below.