council_read was a sandboxed readFile wrapper for .sisyphus/ archives.
Now that council_finalize extracts member responses into plain files,
the standard Read tool serves the same purpose. Removes the tool, its
tests, and updates Athena's prompt to reference Read directly.
task-output-writer wrote to process.cwd()/.sisyphus/task-outputs/ while
council_finalize read from ctx.directory/.sisyphus/task-outputs/. When
these differ, all output files appear missing.
Fix by passing directory to writeTaskOutput from BackgroundManager, and
adding basePath to council_read. Also removes process.chdir() from tests
that was masking the bug.
ismeth