docs: resync with current state across all project docs

- design-guidelines: every dimension was stale — card frame 340x200
  (was 500x220), corner radius 6, title 15px at (20,30), row y0/dy,
  donut centre (250,110) r=55/30, topN=5, legend y0=55 dy=20, bar chart
  area [35,325]x[45,155], area chart [28,312]x[45,150], icon scale 0.75.
- code-standards: FetchContributionsAllTime signature now ctx-first,
  viewbox 500x220 → 340x200.
- codebase-summary: test coverage lists main_test.go +
  TestDonutSingleSlice/Empty; filename convention says plain kebab-case
  (no numeric prefix).
- project-overview-pdr: forks/private defaults now on, not off.
- project-roadmap: add Phase 7 (Marketplace polish — resize, numeric-
  prefix drop, v1 floating tag, rename-rollback). Renumber planned
  phases 8-11. Fix "hard width 500 px" limitation.
- deployment-guide: document update-major-tag job; note
  Marketplace listing name is `ghstats-cards`.

docs/deployment-guide.md

@@ -108,14 +108,20 @@ runs:
 2. `release.yml` runs `go vet` + `go test` as a gate before the docker and
    binaries jobs. If tests fail, no artifacts ship.
 3. On green, GHCR push + cross-platform binary artifacts happen automatically.
-4. Docker base images and third-party actions are SHA-pinned (with version
+4. The `update-major-tag` job force-moves the floating major tag (e.g. `v1`)
+   to this release's commit after test + docker + binaries all pass.
+   Consumers pinned to `tiennm99/ghstats@v1` pick up the release on their
+   next Action run without a workflow edit.
+5. Docker base images and third-party actions are SHA-pinned (with version
    comments) so mutable-tag changes upstream can't rewrite a released image.
-5. **Marketplace publishing (one-time per repo):** GitHub only exposes the
+6. **Marketplace publishing (one-time per repo):** GitHub only exposes the
    "Publish this Action to the GitHub Marketplace" toggle on the Release
    web UI — there is no CLI flag. Open the newly created release at
    `https://github.com/tiennm99/ghstats/releases/tag/vX.Y.Z/edit`, tick the
    marketplace checkbox, accept the terms, and re-publish. Subsequent
-   releases inherit marketplace visibility automatically.
+   releases inherit marketplace visibility automatically. The Marketplace
+   listing name is `ghstats-cards` (set in `action.yml`) because the bare
+   `ghstats` is already taken on the Marketplace.
 
 ## Rollback