On resumed sessions, skipping --append-system-prompt-file (the original
fix) left two secondary issues:
- commandNotes still claimed the flag was injected, producing misleading
onMeta logs on every resumed heartbeat
- The instructions file was still read from disk and a combined temp file
written on every resume, even though effectiveInstructionsFilePath was
never consumed
Hoist canResumeSession before the I/O block and gate both the disk
operations and commandNotes construction on !canResumeSession / !sessionId.
Adds three regression tests: commandNotes is populated on fresh sessions,
empty on resume; and no agent-instructions.md is written on resume.
On resumed sessions the agent instructions are already present in the
session cache. Unconditionally passing --append-system-prompt-file
re-injects 5-10K redundant tokens per heartbeat and may be rejected by
the Claude CLI when combined with --resume.
Guard the flag behind `!resumeSessionId` so it is only appended on
fresh session starts.
Fixes: #2848
