fix: handle [temp] paths in missing-media detection

## Problem

Loader widget values ending in `[temp]` are valid backend paths, but the missing-media detector recognizes only `[input]` and `[output]`. It therefore treats the complete annotated value as an input filename that can never match and surfaces a false Missing Inputs error.

This is reachable when Job Queue falls back to a temp preview and from existing Asset Panel paths.

## Why this needs separate treatment

Adding `temp` to the annotation regex alone is insufficient: the resolver currently has input asset and generated output sources, but no authoritative temp-asset listing. Basename collisions and Cloud/OSS differences need an explicit policy, such as treating temp paths as unverifiable rather than missing.

## Acceptance criteria

- Define how `[temp]` candidates are classified when no authoritative temp listing exists.
- Avoid user-visible false missing-media errors for valid temp paths.
- Cover both Cloud and OSS scan behavior, including basename/subfolder controls.

## Context

Follow-up from #14081 and #14126.