Harden companion for public beta

[twidtwid]

Summary

• consolidate public documentation and move runtime/planning artifacts out of the tracked tree
• bound app-server/native child output, timeouts, termination, and process reaping
• split the native helper into focused modules and cache incremental composer witnesses
• consolidate connected action QA and retain the verified High and native PTT fixes
• remove duplicate release builds while keeping standalone packaging safe

Verification

• npm run release:verify
• 494 tests passed
• zero full/production audit findings
• seven profile pages and 100 hardware-size visual rasters passed with zero design warnings
• Elgato validation and package creation passed
• final plugin and native-helper hashes match the running Sagan installation
• user previously confirmed High selection and native PTT on the attached Stream Deck Plus

Connected gate boundary

Sagan is currently at macOS loginwindow, so no new visible Model/Reasoning/Plan/Fast mutation is claimed for this commit. The installed process and hashes are verified; rerun the connected mutation gate after the Sagan GUI session is unlocked.