docs: sync AGENTS.md with gitea/gitea (#224)

Carries over the applicable rules from https://gitea.com/gitea/gitea `AGENTS.md`, covering test scope, linter escape hatches and PR conventions. Swaps `Co-Authored-By` for the `Assisted-by` trailer.

Reviewed-on: https://gitea.com/gitea/gitea-mcp/pulls/224
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

AGENTS.md

@@ -1,12 +1,16 @@
+- Never assume, verify before claiming
 - Use `make help` to find available development targets
-- Run `make fmt` to format `.go` files, and run `make lint-go` to lint them
-- Run `make tidy` after any `go.mod` changes
-- Run single go tests with `go test -run '^TestName$' ./modulepath/`
-- Ensure no trailing whitespace in edited files
+- PR descriptions: minimal, only what and why, no task lists or file listings
+- Reference issues and PRs by full URL, not by number
 - Use Conventional Commits for commit messages and PR titles, e.g. `type(scope): subject`; `!` before the colon if breaking. Use `test` type for test-only changes.
+- Add an `Assisted-by: AGENT_NAME:MODEL_VERSION` trailer to commit messages, never `Co-Authored-By` or `Signed-off-by`
+- Attribute agent authorship on one trailing line in issue and pull request comments, never as a PR description section
 - Never force-push, amend, or squash unless asked. Use new commits and normal push for pull request updates
-- Preserve existing code comments, do not remove or rewrite comments that are still relevant
-- Keep comments short, prefer same-line, explain why, never narrate code
+- Keep comments short, prefer same-line, explain why, never narrate code. Preserve existing ones that still apply
+- Ensure no trailing whitespace in edited files
+- Run `make fmt` to format `.go` files, `make lint-go` to lint them, and `make tidy` after any `go.mod` changes
+- Fix the cause rather than disabling a linter or weakening a test. Where unavoidable, use the narrowest scope with a trailing comment giving the reason
 - Register new tools with `Tool.RegisterRead` or `Tool.RegisterWrite`, and add them to the tool tables in `README.md`, `README.zh-cn.md` and `README.zh-tw.md`
-- Include authorship attribution in issue and pull request comments
-- Add `Co-Authored-By` lines to all commits, indicating name and model used
+- Run single go tests with `go test -run '^TestName$' ./modulepath/`
+- Write the fewest, fastest tests covering the behavior, extending an existing one where possible. Prefer unit tests where logic is testable in isolation
+- Wait on a deterministic condition rather than `sleep`