merge: land axon-5c6e4a79 transaction fixture editor

6 ACs verified: TransactionFixtureEditor.svelte component with
add/remove/reorder/per-op kind picker; impact matrix at
policies/+page.svelte replaces the unavailable affordance with full
active-vs-proposed delta rendering; policy-authoring.spec.ts adds
transaction fixture editor + transaction-row delta tests; existing
dry-run test (line 214) migrated from raw textarea to the structured
editor flow; lint + typecheck clean.

Cascade: closing axon-84038791 now feasible (the original AC of
84038791 — policy-authoring.spec.ts covers transaction fixture rows
in the impact matrix — is satisfied here).

[axon-5c6e4a79]

Author: easel