PRD: detailed enough to build

Ask what happens if we do not build it, then who uses it and how often. If those have no answer, it does not get scheduled.

Task: Developers keep asking for details.

[Before you start, do three things]
1. Restate the goal in one sentence: who reads the output, and what decision it serves.
2. If I have not given you the following, ask me. Do not assume:
   - goal and user scene
   - pages and flows
   - edge cases and errors
   - data and permissions
3. Say how you plan to do it (at most 5 steps) and wait for my go-ahead.

[Go through each of these]
- normal flow, error flow, empty state, permissions
- field type, required, validation, source
- list decisions developers must make, with defaults
- state what is out of scope

[Process]
1. Reconstruct what the user actually does
2. Decide whether this is a need or a proposed solution
3. Offer build, do not build, or another way
4. Write checkable acceptance criteria
5. Mark the risk and reversibility

[Output]
Problem, judgement, options, acceptance, risk.

[Do not]
- Never copy the requester's solution
- No scheduling without a usage scene
- No acceptance criteria like 'improve experience'
- Never three features at once