docs+ci: GNOME 50 hardcoded in e2e.yml summaries, README, and version-target docs — stale when gnomeos flips to 51

[castrojo]

Context

"GNOME 50" is hardcoded in run-facing strings and docs. The day gnomeos-latest flips to 51 (GA 2026-09-16), summaries and docs report the wrong version:

Location	String
.github/workflows/e2e.yml:1688	## {icon} E2E Results — GNOME 50 ({suite}) summary heading
.github/workflows/e2e.yml:166	job display name 'GNOME 50' — {suite} — ⚠️ see human gate below
README.md:31,100	"GNOME 50+ top-bar fallback", "primary maintainers of GNOME 50 test coverage"
docs/skills/ci-ops/ops/references/fedora-version-targets.md:19	gnomeos row pinned to "GNOME 50"

Tasks

• Replace the e2e summary heading (line ~1688) with a version-neutral string, or interpolate the detected Shell version if the canary step exists
• Make README + fedora-version-targets.md version-neutral or explicitly dual-version (50 = Bluefin, 51 = gnomeos)
• Human gate — do not change without sign-off: the job name: at e2e.yml:166 may be referenced by downstream required checks; renaming is a CI-interface change per docs/skills/meta/human-gates/SKILL.md. Propose in the PR body, let a human decide.

Files owned

.github/workflows/e2e.yml (strings only), README.md, docs/skills/ci-ops/ops/references/fedora-version-targets.md

⚠️ Coordinate: PRs #813/#819 currently touch e2e.yml / gnome-e2e — wait for them to land (file-disjointness rule).

Acceptance

• No behavioral change to e2e.yml — strings/docs only
• All mandatory gates in AGENTS.md
• Conventional Commit title + both AI attribution trailers