feat(sleep): add DeepSeek Harness transcript source

[Nuplum (45lab95)]

feat(sleep): add DeepSeek Harness transcript source

Closes #225

Summary

Add a local, read-only DeepSeek Harness (DSH) transcript source for SkillOpt-Sleep.

The new explicit --source dsh converts DSH JSONL sessions into the existing
SessionDigest and mined-task pipeline. DSH is not added to --source auto,
and this change does not add a DSH backend, plugin, or UI integration.

Changes

• Add a DSH JSONL session harvester supporting:
  • uncompressed session.jsonl;
  • default compressed session.jsonl.zstd;
  • concatenated Zstandard frames;
  • packed chunk records and current DSH lifecycle metadata.
• Keep only human user requests, visible assistant text, short tool names,
  timestamps, and feedback-derived positive/negative signals.
• Exclude reasoning, tool arguments and results, request/provider metadata,
  attachments, feedback text, injected user-role context, subagent sessions,
  and SkillOpt replay sessions.
• Retain ordinary fork sessions without merging parent-session content.
• Silently skip an individual session when its format or event structure cannot
  be safely understood, without blocking other sessions.
• Add CLI, configuration, and documentation support.

Optional dependency

Add the optional extra:

dsh = ["zstandard>=0.22.0"]

zstandard is only needed to read DSH's default .jsonl.zstd session files.
It is not installed for users who do not use DSH, and uncompressed session.jsonl files remain readable without it.
Install with:

python -m pip install -e ".[dsh]"

Validation

python -m pytest tests/test_harvest_dsh.py -q
python -m ruff check skillopt_sleep/harvest_dsh.py tests/test_harvest_dsh.py

• Local DSH Web end-to-end validation:
  • harvested 1 session -> 1 task;
  • completed the mock dry-run pipeline successfully.