- Changed hashline format to canonical `§` section headers and `"`/`"`/`≔` operations across grammar, parser, and docs.
- Reworked range and op parsing so single anchors are valid, legacy `-`/`-=` ops error, and empty `≔` payloads now delete ranges.
- Removed legacy `HL_EDIT_SEP`, `$HSEP$`, and `hsep` plumbing, adopting raw payload lines.
- Updated execution, input, renderer, and streaming flows to use `HL_FILE_PREFIX` and `HL_OP_CHARS` helpers.
- Updated session-stats parsing to `§`/`≔`/`"`/`"` format, patch envelopes, and bumped parser versions.
- Removed the hashline-separator benchmark script and its PI_HL_SEP job orchestration.
- Replaced `===== ... =====` eval cell headers with `*** Begin ` / `*** End ` markers; legacy format remains renderable in HTML exports.
- Replaced hashline patch grammar with `*** Begin Patch` / `*** End Patch` envelope; old inputs without the envelope are still accepted.
- Extracted `sniffEvalLanguage` into a shared `sniff.ts` module reused by the parser and tool.
- Added `docs/ERRATA-GPT5-HARMONY.md` and `scripts/session-stats/harmony_backtest.py` documenting and backtesting the GPT-5 Harmony-header leak defect.
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