Fix All (PR Merge-Readiness Check)

One-shot version of pr-maintenance-loop's hourly cycle — the same checks, the same fixes, the same safety model, just run once instead of on a schedule. Use this when you want an answer right now, or don't want a recurring /loop job at all. Named to match atmos fix --all at the CLI, which runs the mechanical half of the same sequence (sync, ci, threads, lint, coverage) — this skill adds the agent-delegated fixing (CodeRabbit threads, lint findings, test/coverage gaps) that a plain CLI command can't do on its own, plus a code-hygiene pass (step 8) that a plain CLI command structurally can't do either — catching architectural smells (duplicated abstractions, missing sentinel errors, fake/stub features) that lint, tests, and a normal correctness-focused review all miss.

Every check stays scoped to the patch relative to origin/main in which packages it looks at — this never goes hunting for trouble in the other 340+ packages this PR's diff never touched. But within a package a check does look at, a failing test gets fixed regardless of whether this patch's own diff is what broke it — see the test-coverage skill for why "pre-existing" no longer means "don't touch" for test failures specifically.

Precondition