docs(agents): plan, build and review sessions per issue, and a short-output check script

[MendesMat]

What

Documents how an issue is worked on with agents after the lessons of issue #6, and adds check.ps1, a single command that formats, builds and tests with short output.

Why

Issue #6 showed three problems:

• Cost. One long conversation carried the survey, 13 TDD cycles and the review; repeated ENDOFLINE listings and full test logs filled it, and every line is paid again on each reply.
• Improvised decisions. Where the plan was vague, the build step filled the gap by guessing, and one guess contradicted API-12.
• Late review. The review happened after the merge, so its fixes needed a second pull request (fix(api): complete the error mapping and test it through HTTP #23).

What changes

• Three sessions per issue (docs/agents/workflows/implement-a-feature.md, section Sessions and new step 9):
  • plan, ending with a plan comment on the issue: decisions, new messages, and the test list with the expected result of each test;
  • build, which follows that comment instead of repeating the survey;
  • review in a new conversation, before the owner merges.
• Owner's guide (docs/agents/trabalhando-com-agentes.md, in Portuguese): which model and effort to use in each session, what to paste to start each one, when to use pair or autonomous mode, when to switch models, and how to watch the quota.
• check.ps1 (backend/ControlService): runs dotnet format, then the build, then the tests. It prints only problems and summaries, and keeps the whole test output when a test fails, as the evidence of a Red. It replaces the separate commands in AGENTS.md, the testing guide, the git workflow and the backend README.
• AGENTS.md: asks for short tool output, and treats a failed approach from the approved plan as a stop point.
• TDD workflow: commit before each pause and show it in the report.
• Communication guide: the plan comment is part of the normal flow, so it does not need a separate confirmation.

How to test

powershell.exe -NoProfile -File backend/ControlService/check.ps1

Checked on three runs:

• the whole solution: 137/137, exit 0;
• a filtered run: 9/9, exit 0;
• a throwaway failing test written with LF line endings: the endings were fixed silently, the failure was printed in full, and the exit code was 2.

The relative links of every changed document resolve.

Checklist

• Developed test-first (ADR-0033): not applicable, documentation and a tooling script, checked by the runs above
• dotnet test --solution ControlService.slnx passes locally
• Documentation updated (AGENTS.md, docs/agents/, backend README)
• Rule IDs covered or changed: none
• User-facing messages: none