ohm: migrate orphaned subagent transcripts (0019.x, 0026.x) + renumber dup 0046.0 -> 0073

Backfills transcripts that existed only locally in ohm-infra:
- 0019.1/.2/.3 - UX-polish wave subagent transcripts (driver 0019.0 never finalized)
- 0026.1-.9 - security-audit-0026 subagent transcripts (driver abandoned/closed-out by 0068; audit drove published 0030 remediation)
- 0073.0 - PPE/progressive-delivery + engineering-handbook session, originally drafted as a duplicate 0046.0; reassigned next free number (0072 taken by a concurrent session)

sessions.json: add 0019/0073 titles, update 0026 title.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ohm/sessions.json

@@ -50,6 +50,9 @@
   "0018": {
     "title": "Wave 9 \u2014 /docs/specs + nested flyout nav + transcript body-ref rewrite (#30 follow-up, rfc-app v0.20.0)"
   },
+  "0019": {
+    "title": "UX-polish wave \u2014 subagent transcripts only (App.css/header/docs; rfc-app v0.21.0, #31/#24/#25/#32; driver 0019.0 never finalized)"
+  },
   "0021": {
     "title": "Roadmap-capture \u2014 UX-polish items #31 + #32 added"
   },
@@ -63,7 +66,7 @@
     "title": "Claude Haiku propose-RFC tag suggestions (#27, rfc-app v0.24.0 built)"
   },
   "0026": {
-    "title": "(abandoned \u2014 claimed but never finalized; closed out by 0068)"
+    "title": "Security-audit-0026 \u2014 subagent audit transcripts (driver abandoned/closed-out by 0068; audit drove remediation in 0030)"
   },
   "0027": {
     "title": "(abandoned \u2014 claimed but never finalized; closed out by 0068)"
@@ -202,5 +205,8 @@
   },
   "0072": {
     "title": ""
+  },
+  "0073": {
+    "title": "PPE / progressive-delivery design + engineering handbook seed + ohm-rfc ROADMAP Phase F (renumbered from a duplicate 0046.0)"
   }
 }