fix(ci): gazebo runs on every PR — the precondition for requiring it

[avrabe]

Refs #427. Does not promote the context — that is the follow-up, on evidence.

The rule this encodes

A required status check that does not run does not pass by default. It never
reports, and the PR stays blocked forever.

I promoted Gazebo SITL (real gz bridge) to required earlier today with its
stated precondition met — five consecutive green runs on main, the wasm leg
executing 6250 ticks and holding 0.01 m bit-identical to native. It deadlocked
every merge in the repo within minutes:

#426 OPEN BLOCKED
  (zero failing checks — gazebo simply never triggered)

#426 touched only .github/workflows/kani.yml, which was not in the path
filter. Removing the required context returned it to CLEAN instantly.

The precondition I checked was "is this leg meaningful." The one that decides
whether a context can be required is "does it report on every PR." Different
properties.

What this does

Removes the pull_request path filter so the job always runs.

Cost: ~7 minutes of runner time per PR. Against: the only gate in the
repo that flies the actually-published wasm component through real physics and
compares it to native bit for bit. Cheap.

What this deliberately does not do

It does not re-add the required context. The sequence is: land this → observe
the job reporting on a PR that touches none of the old filter paths → then
promote. Promoting on reasoning rather than evidence is what caused the
deadlock, and doing it twice in one day would be hard to explain.

The shape, now that we have both halves

#417	a job that is SKIPPED but reports success — verifies nothing, looks green
#427	a job that is SKIPPED and reports nothing — blocks everything

Same root: a gate whose workflow does not always run. The only shape safe to
require is one that always runs and always reports.

🤖 Generated with Claude Code

https://claude.ai/code/session_01HvusAXYbHLyv3uTzfBcMbG