[arzafran]

Resume could type into the wrong place or reopen the wrong session. This fixes three causes.

• The interrupted-agent banner's Resume typed the resume command into the pane without checking that the shell was at its prompt, so it could land in vim or ssh. It now checks, like the command palette does, and beeps otherwise.
• Two panes in the same folder overwrote each other's resume history, so resume could reopen the other pane's session. Entries are now kept per pane and agent.
• A session-end hook with an unknown id cleared the newest live session on the pane. Now only that id's record is removed.

Two new Python regression tests in tests/test_cli_agent_resume.py. The first commit adds them alone, so CI shows them failing; the second commit has the fix.

Not seen in a running app.

Fixes INC-487