Fix /compact same-line emission (#3)

[koenvdheide]

Summary

• Issue /compact does not fire when copy pasted #3: copy-pasting the emitted /compact\n<instructions> block fired as bare /compact and dropped the instructions, because Claude Code parses the slash command on the first line only.
• Fix: bake /compact into the first line of the §4 schema, on the same line as goal:.
• Default output flipped from multi-line to single-line (|-separated). Multi-line still allowed for pre-paste inspection.
• Dropped the > blockquote wrapper in §5 (terminal copy-paste hazard flagged by Codex red-team).

Closes #3

Test plan

• bash test/run-tests.sh passes (91/91)
• Reviewer agent: clean (subslot keys consistent across §4 schema and §5 instructions; no stale references)
• Codex red-team: 4 clear-wins applied (drift/redundancy from first pass, blockquote hazard); 3 tradeoffs documented
• Manual: invoke /prep-compact:prep-compact, copy the emitted block, verify /compact ... fires as a slash command and the instructions land in the compact prompt

🤖 Generated with Claude Code