## Why
Managed stderr logs previously retained a tail only before a new launch, allowing logs to grow during a long-running process. Direct stderr writes could also block lifecycle operations on disk I/O.
## What changed
- Route managed app-server and updater logs through a shared nonblocking worker with a bounded queue. Drop records when the queue is full or a record exceeds 16 KiB, and avoid waiting for the worker at shutdown.
- Prune live logs when they exceed 1 MiB, preserving the latest 256 KiB in `.log.previous` before truncating the current file. Keep inherited stderr handles usable after truncation.
- Pause predecessor pruning during Windows updater handoff and resume it after a failed handoff only when ownership has been restored.
- Keep ordinary stderr output when managed logging has not been initialized.
## Testing
Add regression tests for stalled workers and queue overflow, tail retention, inherited append and nonappend handles, and pruning exclusion during updater handoff.
GitOrigin-RevId: b6301962b1180fa6cdb231a56edce2429dc20b54
## Why
Detached launches truncate stderr logs, losing details from previous failures. Updater handoffs can also leave existing writers with stale offsets after truncation.
## What changed
- Record daemon lifecycle and update stages with timings, outcomes, and typed OS errors, omitting error messages and context.
- Preserve the last 256 KiB of nonempty stderr logs before truncation and use append handles to prevent gaps during handoff. Preservation failures do not block launch.
- Attach current and previous updater log tails when log inclusion is enabled for a report, with a 512 KiB total limit and legacy filename fallback. Skip missing, empty, and nonregular files.
## Testing
Add regression coverage for diagnostic error redaction, bounded log preservation, append behavior during handoff, attachment selection, and updater logs in captured report uploads.
GitOrigin-RevId: 918317022ab9dcfd1b13d676872706c77e9ffbb2
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