F4 SLICE-5: host E2E (propose/accept/reject/persist/stale/coexist) + seam fix: event-level net-effect matching survives host word-diff splitting (INV-9) (#12)

The accept E2E exposed a latent F3 limitation: VS Code word-diffs one
applied WorkspaceEdit into several minimal hunks when old/new share
interior tokens, so the registry's per-hunk exact match missed and seam
edits fell through as fragmented human spans. PendingEditRegistry.match
is replaced by matchEvent (all hunks inside the registered full range +
equal net delta — one applyEdit is one change event). Plan AMENDMENT 1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

test/e2e/suite-no-workspace/noWorkspace.test.ts

@@ -25,6 +25,9 @@ suite("no-workspace activation (#8)", () => {
       "cowriting.editSelection",
       "cowriting.toggleAttribution",
       "cowriting.applyAgentEdit",
+      "cowriting.acceptProposal",
+      "cowriting.rejectProposal",
+      "cowriting.proposeAgentEdit",
     ]) {
       assert.ok(all.includes(command), `${command} is registered`);
     }