docs: point the install one-liner at v0.4.1 #375

docs: point the install one-liner at v0.4.1

Component: the edited files are existing files at the repository root, in docs/ and in scripts/. No new files.

v0.4.1 is published (https://github.com/DanielNetzer/forgecell/releases/tag/v0.4.1), built from main 56fb4c2. Its anonymous install is verified. This follow-up is the same as #368/#370 for v0.4.0.

Change (text only): every reference that names the current pinned release moves from v0.4.0 to v0.4.1:

• README.md:
  • line 31, the downloadable release;
  • the installer <summary> line;
  • the one-liner URL (.../download/v0.4.1/install.sh);
  • "pins the published public-core v0.4.1 release";
  • "The v0.4.1 release defaults to…".
• docs/install.md:
  • line 3 ("Public CLI v0.4.1 release");
  • the one-liner URL;
  • the Lab-directory sentence;
  • "The command above pins v0.4.1.";
  • "The pinned installer uses … the v0.4.1 tag."
• scripts/test-native-installer.py: public_url points at v0.4.1.

Keep unchanged the sentences saying when plugins first shipped, because they stay true and TestMoleculeFindingsDocs pins them:

• README "v0.4.0 also ships the plugin runtime with bundled GitLab (forge), Jira (tracker) and forgecomments (reviewer) plugins";
• install.md "GitLab and Jira ship in the v0.4.0 release" and "Outside reviewers (review bots and other reviewer plugins) ship in the v0.4.0 release";
• install.md "v0.4.0 adds plugins: …";
• lab/plugins/README.md.

In the versions paragraph, append after the "v0.4.0 adds plugins…" sentence: "v0.4.1 hardens them: plugin pin, the plugin new skeletons, forgecomments severity markers, and intake for new Markdown files."

Scope: README.md, docs/install.md, scripts/test-native-installer.py.

Done when

• No reference in these three files names v0.4.0 as the pinned or downloadable release, and the release-history sentences above are byte-identical.
• The Formula baseline checks pass, with no protected delta.

Plan checks for this slice

Use only the Formula baseline checks; no candidate Go test is needed because no Go code changes. Every plan check leaves reviewedAcceptance and independentProvenance empty.