fix: start Claude from ~/code to load root CLAUDE.md correctly

Both issue-automation and postmortem pipelines were cd'ing into
~/code/infra before running Claude, missing the root CLAUDE.md
with beads config and project-wide instructions. Now cd to ~/code
and use relative agent paths from there.

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/postmortem-pipeline.sh

@@ -53,8 +53,8 @@ echo "SSH key fetched"
 # 6. SSH to DevVM and run Claude Code headless
 TODOS=$(cat /tmp/todos.json)
 ssh -i /tmp/devvm-key -o StrictHostKeyChecking=no wizard@10.0.10.10 \
-  "cd ~/code/infra && git pull && ~/.local/bin/claude -p \
-    --agent postmortem-todo-resolver \
+  "cd ~/code && git -C infra pull && ~/.local/bin/claude -p \
+    --agent infra/.claude/agents/postmortem-todo-resolver \
     --dangerously-skip-permissions \
     --max-budget-usd 5 \
     'Implement the auto-implementable TODOs from $PM_FILE. Parsed TODO list: $TODOS'"