* fix(config/sessions): narrow reply-session initialization revision to identity fields
The initialization guard compared the full persisted session entry, so
background touches to updatedAt, heartbeat timestamps, context-budget
metadata, etc. produced false-positive stale-snapshot conflicts and the
"reply session initialization conflicted" error.
Only sessionId and sessionFile matter for detecting a session rotation.
Narrow the revision to those identity fields and add a regression test.
Fixes#98672
* fix(config/sessions): merge current metadata when reply-init identity guard passes
* fix(config/sessions): preserve only snapshot-drifted metadata in reply-init commit
* fix: preserve cleared reply-session metadata
* fix: allow same-session reply initialization drift
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Co-authored-by: moguangyu5-design <moguangyu5-design@users.noreply.github.com>
Co-authored-by: Josh Lehman <josh@martian.engineering>
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