Test hardening: regression tests, guard checks against weakened tests, CODEOWNERS

.github/CODEOWNERS

@@ -0,0 +1,13 @@
+# Pull requests that touch these files need a maintainer's approval (branch
+# protection: "Require review from Code Owners"). They hold recorded results,
+# the tests that pin formulas to their papers, and the CI that runs them; a
+# pull request must not edit them to make itself pass.
+/test/regression/                         @Hananel-Hazan
+/test/api_surface.json                    @Hananel-Hazan
+/test/regen_api_surface.py                @Hananel-Hazan
+/test/test_api_surface.py                 @Hananel-Hazan
+/test/network/test_all_classes.py         @Hananel-Hazan
+/test/network/test_learning_rule_specs.py @Hananel-Hazan
+/test/network/test_mstdp_florian.py       @Hananel-Hazan
+/test/network/test_perf_equivalence.py    @Hananel-Hazan
+/.github/                                 @Hananel-Hazan

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,30 @@
+## What this changes and why
+
+<!-- One or two sentences. Link the issue if there is one. -->
+
+## Checklist
+
+- [ ] I ran `poetry run pytest` locally and it passed.
+- [ ] If I fixed a bug, this test fails on `master` and passes with my change
+      (checked by the `bug-test` check): `test/...::test_...`
+- [ ] I did not remove tests, remove checks, add skips or xfails, or widen
+      tolerances. If I did, I explain each one below (the `weakened-tests`
+      check lists them).
+- [ ] If I changed a formula (a neuron update, a learning rule, a connection's
+      compute), this test pins the new formula: `test/...::test_...`
+- [ ] Does this change simulated results (spikes, voltages, traces, weights)?
+      - [ ] No.
+      - [ ] Yes. I regenerated the golden files in `test/regression/` with
+            `--reason`, and explain below why the results changed. (Results-changing
+            fixes are released in 0.4.0, not 0.3.x; see `CONTRIBUTING.md`.)
+- [ ] Did any of these files change? If yes, say which and why:
+      - golden files under `test/regression/`
+      - operation-count file under `test/regression/` (if present)
+      - `test/api_surface.json` (public API)
+      - `KNOWN_BUGS` in `test/network/test_all_classes.py`
+- [ ] I added an entry to the `Unreleased` section of `CHANGELOG.md`.
+- [ ] If I used an AI tool to write or find this change, I name it here:
+
+## Why the results or the API changed (if they did)
+
+<!-- Which file changed, which numbers moved, and why the new numbers are right. -->