Slice: Route standard undo and redo through Echo causal history

[flyingrobots]

Goal

Make standard u and ctrl+r forward causal operations derived from Echo-retained history, with no process-local snapshot stack or request-to-receipt map acting as authority.

Acceptance criteria

• Production undo does not use EditorState.undoStack snapshots to decide replacement bytes.
• u selects an exact retained causal receipt from the buffer worldline and requests an installed-contract inverse from Echo.
• The inverse is admitted as an ordinary forward intent whose receipt cites the inverted transition and the validated current-basis receipt set.
• ctrl+r inverts the admitted undo receipt rather than restoring a process-local redo snapshot.
• Terminating and reopening Jim reconstructs undo/redo availability and reversal provenance from Echo WAL/WSC history.
• Process-local stacks and maps, if retained for navigation performance, are disposable projections rebuilt from retained causal evidence.
• Missing receipts, retention gaps, stale bases, unmappable spans, and contract-version mismatches surface typed obstructions and never silently fall back to snapshot undo.
• Restart witnesses prove edit -> undo -> redo and edit -> terminate -> reopen -> undo without process-owned authority.

Dependencies

• Contract Inverse Admission Hook echo#472
• Admit contract-defined inverse intents from causal history echo#659
• Expose bounded causal receipt history to applications echo#660
• Slice: Route normal editor edits through replaceRangeAsTick #224
• Slice: End-to-end causal rope open edit save restart recovery #251

Non-goals

• Do not delete or rewrite prior transitions.
• Do not use Git history as editor undo authority.
• Do not treat cursor movement as a text mutation.
• Do not retain full-buffer snapshots merely to implement undo.

[coderabbitai]

🔗 Related PRs

#23 - feat(echo): add Echo release gate witness [closed]
#120 - Feat: add Vim normal state machine [closed]
#195 - Add honest why observation coordinates [merged]
#205 - Document graph-backed rope runtime gate [merged]
#268 - WF-0154 - E-Brake: Observed Absurdity Fixes (cycle) [merged]

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