docs(tdd): make the spine language-neutral, add four language references

The discipline in tdd was already language-agnostic; the checklist under it was
not. A Python user inherited a mandatory `go test -race` box they can never tick
and never got told that `mypy --strict` belongs in the red gate.

Per #18's own comment and writing-skills' Multi-Language Dilution warning, the
main SKILL.md keeps ONE canonical inline example (Go, the default stack) and the
other four languages live in reference files: python, typescript, rust, java.

The RED run drove every change. A subagent given a Python task with the Go-only
skill reported, in its own words:

- "Everything from L169 to L244 is Go-only, and the verification checklist at
  L326 silently inherits that Go-ness — which is why a Python user ends up with
  a mandatory box (-race) they can never tick and a required gate (mypy
  --strict) that isn't listed at all."
- "For a brand-new function, the first RED is always a collection-time
  ImportError... The only clean resolutions are a stub that raises
  NotImplementedError (production code before a red test?) or accepting
  ImportError as a legitimate red. The skill picks neither, and this is the
  single biggest gap." It now picks: that red is legitimate, and writing a stub
  to satisfy the runner is the Iron Law with extra steps.
- The Go table-driven exemplar branches on a `wantErr` column inside the loop.
  Translated literally that is a conditional assertion folding two behaviours
  into one test — which this skill's own quality table forbids. The agent caught
  itself mid-translation; both SKILL.md and python.md now say not to port it.

Also: the checklist names the static-analysis gate per language instead of
assuming `go vet`, and says to strike the concurrency box deliberately where no
equivalent exists — a box that cannot be ticked teaches people to skip
checklists.

Refs #18
Bump-Type: minor

skills/tdd/SKILL.md

@@ -100,13 +100,21 @@ go test -run TestRetryOperation_RetriesThreeTimes ./...
 ```
 
 Confirm:
-- Test fails (not compilation errors)
-- Failure message is expected
-- Fails because feature is missing (not typos)
+- Test fails, and fails because the feature is missing
+- The failure message is the one you expected
+- It is not failing on a typo in the test itself
 
 **Test passes?** You're testing existing behavior. Fix test.
 
-**Compilation errors?** Fix errors, re-run until it fails correctly.
+**Failing because the thing does not exist yet?** That is a legitimate red — a Go
+compile error for an undefined function, a Python `ImportError` for a module you have
+not written, a TypeScript "cannot find module". Read the message, confirm it names the
+unit you are about to build, and proceed to GREEN. **Do not write a stub to make the
+runner happier.** A stub is production code written before a failing test, which is the
+Iron Law with extra steps.
+
+**Failing on a typo or a broken import elsewhere?** Different thing. Fix it and re-run
+until the failure is the one above.
 
 ### GREEN - Minimal Code
 
@@ -166,6 +174,23 @@ Keep tests green. Don't add behavior.
 
 Next failing test for next behavior.
 
+## Other languages
+
+The discipline above is language-neutral; the examples below it are Go, because Go is
+this fleet's default stack and one good example beats five mediocre ones.
+
+For anything else, the per-language conventions live in reference files — load the one
+you need rather than translating Go idioms by eye. Translation is where the mistakes
+happen: the Go table-driven exemplar below branches on a `wantErr` column inside the
+loop, which is idiomatic Go and an anti-pattern in pytest, where it produces a
+conditional assertion and folds two behaviours into one test.
+
+- `references/python.md` — pytest, `@pytest.mark.parametrize`, `mypy --strict` in the
+  RED gate, `pytest.raises(..., match=)`, fixtures vs helpers
+- `references/typescript.md` — vitest/jest, `it.each`, `expect(...).rejects`
+- `references/rust.md` — `#[cfg(test)]` modules, table-driven via arrays, `#[should_panic]`
+- `references/java.md` — JUnit 5, `@ParameterizedTest`, `assertThrows`
+
 ## Go-Specific TDD Notes
 
 ### Table-Driven Tests (Preferred Pattern)
@@ -329,8 +354,14 @@ Before marking work complete:
 - [ ] Watched each test fail before implementing
 - [ ] Each test failed for expected reason (feature missing, not typo)
 - [ ] Wrote minimal code to pass each test
-- [ ] All tests pass: `go test ./...`
-- [ ] Race detector clean: `go test -race ./...`
+- [ ] All tests pass
+- [ ] The language's static gate is clean — `go vet`, `mypy --strict`, `tsc --noEmit`,
+      `cargo clippy`. A red type-check is a red build; it does not wait for GREEN.
+- [ ] The language's concurrency gate is clean **where one exists and applies** —
+      `go test -race`, `cargo test` under Miri for unsafe code. There is no equivalent
+      for a pure Python function, and a checklist box that can never be ticked teaches
+      people to skip checklists. Tick it or strike it deliberately; do not leave it
+      hanging.
 - [ ] Tests use real code (mocks only if crossing a system boundary)
 - [ ] Edge cases and errors covered