agentv import codex: add --session-id support for parity with claude and copilot

[christso]

Problem

PR #946 adds agentv import subcommands for three providers: Claude, Codex, and Copilot. However, --session-id support is inconsistent:

Provider	--session-id	--discover latest	--list
Claude	✅	✅	✅
Codex	❌	✅	✅
Copilot	✅	✅	✅

All three upstream tools support session-based resume by UUID:

• claude --resume 88d69b63-081e-44a8-b9d7-38fe96307af1
• codex resume 019d5cff-9f02-7bc3-8f98-2071ba17ef0e
• copilot --resume=9ca6d90c-1d80-40d1-b805-c59ee31fc007

Since Codex sessions have UUIDs (visible via agentv import codex --list), there's no reason agentv import codex --session-id <uuid> shouldn't work.

Expected

agentv import codex --session-id <uuid> should import a specific Codex session, matching the behavior of the Claude and Copilot import commands.

Related

• PR feat: transcript import pipeline — grade existing sessions offline #946