Electron Releases

PRs and pushes that only touch build/pgo_profiles/*.pgo.txt now skip CI entirely and go green immediately. The state files are machine-written pointers to profiles on dev-cdn (soon written by the automated pgo/update/* PRs from #51881); no CI job exercises them and they cannot break a build, so a full build/test matrix on every profile roll is wasted compute.

• src filter excludes the state files, so all checkout/build/test/gn-check jobs skip; the exclusion lives inside the single negated brace pattern because paths-filter ORs patterns (a second negated pattern would re-include everything the first excluded - verified against the pinned action's picomatch matcher)
• new pgo-only setup output gates lint; the required lint / Lint check reports skipped, which branch protection treats as satisfied
• checkout-linux previously ran unconditionally to serve the docs-only compile; it is now gated on src || docs-only so pgo-only changes skip its 32-core sync too (every other consumer is already src-gated)
• gha-done already runs always() and goes green when all needs are skipped, so the required GitHub Actions Completed check passes
• anything else in build/pgo_profiles/ (README, .gitignore) still counts as src and runs full CI, as does any PR mixing state files with other changes

Notes: none