The close stage's checkout-only template fallback is removed

[sameera]

As an adopter running close in my own repository, I want the stage to fail loudly rather than reach into a Nexus checkout, so that a missing template is a diagnosable error rather than a path that silently cannot exist for me.

Acceptance Criteria

• Given the close stage body, when it is read, then it names no template path outside the project's own configuration.
• Given a repository whose close-record template is missing, when the close stage reaches the step that reads it, then it reports the absent template by path and names the remedy, rather than falling back.
• Given the whole component payload, when it is searched for a read or a fallback resolving under the Nexus repository's own template master directory, then there are none — a passage that names that directory only to say it is not what a stage reads is not a match.

Notes

The fallback is one clause in .claude/commands/nxs.close.md: read the seeded project template, and if absent fall back to common/templates/close-record-template.md. That master directory is part of the Nexus source checkout and ships in no payload, so for every adopter the fallback is a path that cannot resolve.

Removing a fallback usually widens failure. Here it narrows it: the fallback only ever succeeded for a person running close inside the Nexus repository, and Story 1 removes the condition that made it necessary.

The two stories are ordered — the fallback goes after the seeding lands, not before, so there is no window in which close has neither a seeded template nor a fallback.