The read_file device guard now walks symlink hops before the file operation
layer, but that hop walk still interpreted relative paths against the Python
process cwd. In sessions where TERMINAL_CWD points at the task workspace, a
relative workspace symlink to a blocked alias such as /dev/../dev/stdin could
therefore miss the intermediate device target before later task-cwd resolution.
Anchor relative device checks to the task base before symlink-hop inspection so
the pre-I/O guard sees the same workspace path that read_file would otherwise
read. Absolute device paths and the existing final realpath fallback remain
unchanged.
Refs #10141
Refs #29158
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