Make plugin feedback lightweight

[mattheliu]

What changed

• replace the multi-command feedback flow with one compact 插件反馈 entry
• keep probe, verdict, category, and preview actions out of Session history
• append exactly one durable, model-invisible feedback card after explicit submission
• use a narrow typed RPC path so intermediate actions never create command rows
• retain legacy commands for compatibility while shortening their output
• document the lightweight privacy boundary and bump the package to 0.4.2

Verification

• pnpm test:all
• 26 client/unit tests passed
• 10 backend tests passed
• server build passed
• real DSH 0.1.0-rc.6 plugin E2E passed
• manual browser verification: no intermediate Session rows, one card after submit, card survives reload

Privacy boundary

The submitted record contains only closed, previewed fields. It excludes the current task, conversation, prompts, replies, logs, stack traces, files, paths, environment values, and identity fields.