fix(#2136): migrate ALL operator-facing date sites to localToday (anti-pattern elimination)

The UTC-slice anti-pattern (deriving a calendar day a human reads by slicing a
UTC instant) remained in several operator-facing sites beyond the original
seamed last_activity set. Eliminate it everywhere a human reads the value as a
calendar day — do not leave known bad code in place:

- commands.cts cmdTodoComplete + cmdScaffold: completion/scaffold dates.
- gsd2-import.cts: migrated STATE.md 'Last activity' / 'Last session'.
- template.cts: plan frontmatter 'completed:' date.
- verify.cts: health --repair session-log date + '(Backfilled: <date>)' header.
- workstream.cts: workstream-create 'Last Activity' / 'created' + archive dirname.
- init.cts: JSON-bundle 'date' (-> localToday) + 'timestamp' (-> nowIso) at all
  three sites; drop the now-dead 'const now = new Date()' in cmdInitTodos /
  cmdInitMapCodebase (cmdInitQuick keeps it for the local branch-id derivation).
- state.cts: prune-archive '## Pruned <date>' header.
- state-transition.cts: the 7 seamed last_activity writes (prior commit).

No realClock.today() / .clock.today() / raw new Date().toISOString().split('T')
operator-facing sites remain in src/. Rebuilds the tracked
bin/lib/state-transition.cjs artifact to match.

src/workstream.cts

@@ -14,6 +14,7 @@
 
 import fs from 'node:fs';
 import path from 'node:path';
+import { realClock } from './clock.cjs';
 // eslint-disable-next-line @typescript-eslint/no-require-imports
 import io = require('./io.cjs');
 const { output, error } = io;
@@ -177,7 +178,7 @@ function cmdWorkstreamCreate(cwd: string, name: string | null | undefined, optio
   platformEnsureDir(wsDir);
   platformEnsureDir(path.join(wsDir, 'phases'));
 
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.localToday();
   const stateContent = [
     '---',
     `workstream: ${slug}`,
@@ -297,7 +298,7 @@ function cmdWorkstreamComplete(cwd: string, name: string | null | undefined, opt
   if (active === name) setActiveWorkstream(cwd, null as unknown as string);
 
   const archiveDir = path.join(root, 'milestones');
-  const today = new Date().toISOString().split('T')[0];
+  const today = realClock.localToday();
   let archivePath = path.join(archiveDir, `ws-${name}-${today}`);
   let suffix = 1;
   while (fs.existsSync(archivePath)) {