feat(mutations): enforce state-transition invariants and fix migration paths

[Fury03]

Summary

Adds a formal state-transition matrix to the mutation storage layer that prevents illegal status transitions, and fixes several migration/recovery paths that violated it.

Changes

src/lib/mutationStorage.ts

• LEGAL_TRANSITIONS matrix: Formal definition of all legal MutationStatus transitions (idle → pending → submitting → success/error, with retry and cancel paths)
• validateStateTransition(): Validates transitions against the matrix
• updateMutationOperation(): Now rejects illegal transitions — returns the unmodified operation and logs a warning instead of persisting unauthorized state
• CreateMutationOptions.migrationStatus: New option on createMutationOperation that allows creating operations directly in a terminal status (e.g. success) for migrating legacy records that are already completed

src/lib/bondActionStorage.ts

• migrateRecordToMutationSystem(): Fixed to use migrationStatus when creating operations from legacy records with terminal states. Previously tried pending → success which is illegal; now creates directly in the target state.

src/lib/mutationRecovery.ts

• recoverOperation(): Now transitions idle → pending before setting error (matrix requires it)
• executeOperationAttempt(): Now transitions error/idle → pending before submitting (matrix requires error → pending → submitting)

src/hooks/useEnhancedBondMutations.ts

• reset(): Unlinks legacy records (operationId, migratedToV2) without trying to modify terminal states in the unified system

State-Transition Matrix

idle ──▶ pending ──▶ submitting ──▶ success
             │            │
             ▼            ▼
          error ◀───── error
             │
             ▼
         pending (retry)

Terminal states (no outgoing edges): success, cancelled

Invariants Enforced

• Terminal states (success, cancelled) are immutable — no code path can transition out of them
• Illegal transitions are rejected at the storage layer (nothing persisted)
• Migration of legacy terminal-state records uses migrationStatus to bypass the normal lifecycle
• All recovery paths respect the matrix (idle → pending before error, error → pending before submitting)

Testing

• 27 state-transition matrix tests passing (all legal + illegal transitions verified)
• 12 migration/recovery flow tests passing
• Known issue: vitest crashes with Bus error (core dumped) on Node v24.18.0 (jsdom compatibility); tests verified via extracted pure-logic test harness

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Co-Authored-By: Codebuff noreply@codebuff.com