Unify hashline_edit input with replace/append/prepend + pos/end/lines semantics so callers use a single stable shape. Add normalization coverage and refresh tool guidance/tests to reduce schema confusion and stale legacy payload usage.
- maybeExpandSingleLineMerge now uses stripTrailingContinuationTokens and
stripMergeOperatorChars as fallback matching strategies
- Add 'refs interpreted against last read' atomicity clause to tool description
- Add 'output tool calls only; no prose' rule to tool description
- Rewrite restoreOldWrappedLines to use oh-my-pi's span-scanning algorithm
- Add stripTrailingContinuationTokens and stripMergeOperatorChars helpers
- Fix detectLineEnding to use first-occurrence logic instead of any-match
- Fix applyAppend/applyPrepend to replace empty-line placeholder in empty files
- Enhance tool description with 7 critical rules, tag guidance, and anti-patterns
