feat(test-fix): add iterative run-diagnose-fix loop skill

Reuses the test skill for discovery and owns the loop after the first
red result: one root cause and one fix per iteration, with explicit
stop conditions so a stuck loop reports instead of thrashing. Skipping
or loosening tests is a report item, never a fix.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

skills/test-fix/SKILL.md

@@ -0,0 +1,95 @@
+---
+name: test-fix
+description: >
+  Run the project's Makefile test targets in a loop - run, diagnose, fix, re-run -
+  until every selected target is green or the loop is provably stuck. Trigger on
+  /test-fix or when the operator asks to make the tests pass, fix the failing
+  tests, or get the suite green. Portable across projects.
+---
+
+Same target discovery and selection as the `test` skill - invoke it for step 1
+and step 2 rather than reimplementing the grep and the selection list. This
+skill owns what happens after the first red result: the fix loop.
+
+The contract is narrow: the code becomes correct, the tests stay honest.
+
+## The loop
+
+One iteration is: run -> read the failure -> one root cause -> one fix ->
+re-run. Never batch several speculative fixes into one iteration; a green run
+after three simultaneous changes proves nothing about which one mattered.
+
+### Run
+
+Run the failing target alone, not the whole selection - the fastest command
+that reproduces the failure. Widen back to the full selection only when that
+target is green.
+
+### Diagnose
+
+Read the actual error output before touching a file. Apply the `triage` skill
+to reach a verified root cause; for a failure whose cause is genuinely unclear
+after one look, apply `dialectic` rather than guessing twice.
+
+Decide explicitly which side is wrong, and say so in one line before editing:
+
+- **Code is wrong**: the test states the intended behaviour. Fix the code.
+- **Test is wrong**: the test encodes an outdated or incorrect expectation.
+  Fixing it is allowed *only* with a stated reason for why the old expectation
+  was wrong - never because the code disagrees with it.
+- **Environment is wrong**: missing dependency, stale container, absent env var,
+  unbuilt artefact. Fix the environment or report it; do not patch code around
+  a broken environment.
+
+### Fix
+
+Smallest change that addresses the root cause. Follow the project's existing
+idioms and the `no-defaults` and `comments-clean` rules.
+
+Forbidden, in every iteration, without explicit operator approval:
+
+- deleting, skipping, `xfail`-ing, or commenting out a failing test
+- loosening an assertion to whatever the code currently produces
+- catching or swallowing the exception the test was written to surface
+- adding retries, sleeps, or reruns to paper over a flaky failure
+- disabling a linter rule, a type check, or a test target from the selection
+
+Any of these is a report item, not a fix. A suite that is green because the
+failing test no longer runs is a regression disguised as success.
+
+### Re-run
+
+Re-run the same target. Then, once it passes, re-run every target that was
+already green - a fix that breaks a neighbouring suite is not a fix. Only
+after the full selection is green is the loop done.
+
+## Stopping
+
+Stop and report, without asking for permission to stop:
+
+- **Green**: full selection passes. Report and stop.
+- **No progress**: the same failure survives 3 iterations, or the failure count
+  stops falling across 3 iterations. Report the root cause reached so far, what
+  was tried, and why each attempt failed.
+- **Fix exceeds the mandate**: the real fix is an API change, a dependency bump,
+  a schema migration, or a redesign. Name it, show the minimal diff it would
+  need, and let the operator decide.
+- **Oscillation**: fixing A re-breaks B and vice versa. Report both with the
+  conflict between them - that is a design problem, not a test problem.
+- **Flaky**: a target passes and fails without any change between runs. Report
+  it as flaky with both outputs; never "fix" it by rerunning until green.
+
+Never loop silently. Emit one line per iteration: target, failure, hypothesis,
+change made.
+
+## Report
+
+- Per iteration: what failed, the root cause, the fix, the result.
+- Final state of every selected target, pass or fail, with the verbatim output
+  of anything still failing.
+- Everything deliberately not done: tests judged wrong but left alone,
+  environment issues, out-of-mandate fixes.
+- The exact command reproducing the final state.
+
+State calibrated confidence in the fixes per the `confidence` skill. Do not
+commit unless the operator asked for a commit.