Demote the FSE snapshot build script to a debug CLI

[kuuak]

Parent

#132

What to build

A way for a developer to dump the current FSE snapshot for inspection, now that nothing generates it as a build artifact.

The snapshot is a large derived structure — for a real project it runs to hundreds of kilobytes across a dozen templates and over a thousand blocks, with template parts inlined and translation variants grafted on. When a page renders wrong, being able to dump and diff it is the fastest route to the cause.

The existing build script becomes a thin command-line caller of the shared snapshot builder. It must write outside the app's source tree, to an ignored path — if it keeps writing where the old build artifact lived, someone will import it again within a year and the codebase will have two sources of truth that silently diverge.

Acceptance criteria

• Running the script writes the current snapshot to an ignored debug path outside the app source tree
• Nothing is written to the directory that previously held the build artifact
• No import of a snapshot file exists anywhere in the codebase
• The script is wired to no dev or build lifecycle hook

Blocked by

• Serve the FSE snapshot from a runtime cache instead of the build #134