fix(mobile): carry resumeId through the phone overview's past rows

#386 made Codex conversations resumable from Past Sessions, and
resumeMobileOverviewSession() correctly passes row.resumeId on to
resumeHistorySession(). The phone's own row projection never copied the
field off the unified-list item though, so row.resumeId was always
undefined there and a tapped Codex row started a FRESH session on a thread
that was already on disk. The desktop path worked; only the phone was blind.

The test fails without the projection line, and pins the other half too: a
claude row must not grow a resumeId, since the field is what distinguishes
"resume this conversation" from "start a new one".

Docs: CLAUDE.md and architecture-invariants both still described the unified
list as merging Claude transcript files. It has been three stores since this
PR (Claude's ~/.claude/projects, omp's ~/.omp/agent/sessions, codex's
~/.codex/sessions), the alias field keeps its Claude-era name without being
Claude-only, and the scanner-only rule behind resumeId was written down
nowhere.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/web/public/mobile-overview.js

@@ -228,6 +228,11 @@ Object.assign(CodemanApp.prototype, {
           name: item.name || '',
           title: title || item.name || dir.split('/').pop() || item.sessionId.slice(0, 8),
           mode: item.mode || 'claude',
+          // Only the scanner sets this, and only for a codex rollout. Dropping it here
+          // is not cosmetic: resumeMobileOverviewSession() passes row.resumeId on to
+          // resumeHistorySession(), so without it a tapped Codex row starts a FRESH
+          // session on a thread that is already on disk.
+          resumeId: item.resumeId || undefined,
           caseName: matched ? matched.name : '',
           dir: this._shortenHomePath ? this._shortenHomePath(dir) : dir,
           at: item.lastActivityAt || item.createdAt || 0,