* ci: codegraph test-selection probe (observe-only)
Asks the codegraph service which test files and matrix jobs the PR
needs and writes the decision to the job summary. Gates nothing —
every path exits 0, forks without secrets no-op. Companion to the
shadow-mode evaluation: the decision CI would act on, made visible
next to the runs it would have replaced.
* chore: remove GitNexus CI and deployment configs
Superseded by the codegraph service: the index workflow spent ~45min
per invocation building an artifact the PR flow never served, while
the replacement indexes incrementally in ~1.4s per commit server-side.
Removes the four workflows (index, deploy, cleanup-pr, pr-command) and
the .do/gitnexus deployment bundle. No remaining references.
* ci: render playwright spec tiers in the codegraph probe summary
