fix: Studio declarative authoring manifest

[Hacks4Snacks]

What changed

1. Studio opens a declarative authoring manifest.
The reported file was a tmforge-manifest (the reviewable source tmforge apply builds
from), not a model. No registered format claims it, so detect returned null, the Editor
fell back to tmforge-json, and the reader threw "Not a tmforge-json document."

• ManifestSupport.LooksLikeManifest — strict recognizer (requires an explicit schema).
• AuthoringService.ApplyManifestJson — builds a manifest supplied as text; returns a
  blocking problem on the result rather than throwing.
• Exposed on every surface: POST /v1/model/manifest, WASM ApplyManifest, and
  IEngineClient.applyManifest on all three Studio clients (offline rejects honestly).
• Editor resolves Open/Import through one readDocument: detect → manifest → fallback.

2. The CLI reports unusable input instead of crashing.
tmforge open <manifest> produced an unhandled exception, a full crash dump, and exit 134.
18 commands load a model through CliModelLoader and none guarded it. Program.Main now
classifies input failures, prints one line, and exits 1. CliModelLoader additionally names
a manifest and points at apply.