ci: bump functionalscript bootstrap version and nixpkgs snapshot - #1621

The pins are all correct — the findings are in the title and body, which become the squash commit.

No Changelog: section in the description. CONTRIBUTING.md:201 and AGENTS.md:88 make it mandatory either way. A CI pin bump changes no behavior or public API, so Changelog: none is the right content — and correspondingly no entry file, which this PR correctly doesn't add.

Title isn't <topic>: <short description>. "Upgrade FunctionalScript to 0.45.0 and update nixpkgs" — no topic prefix, no colon (CONTRIBUTING.md:178). The branch commit acc1800 is already phrased correctly (ci: bump functionalscript bootstrap version and nixpkgs snapshot), but the squash discards it.

Minor: the body says the version appears in "10 occurrences" in ci.yml; it's 11 (six npm install -g, two deno, two bun, and one more npm at line 444).

Pins verified:

• functionalscript@0.45.0 is published and is latest. Released from this repo — 8804e78 0.45.0 (#1555), 2026-08-14. package.json also reads 0.45.0, but that's the release commit bumping it to the released version, so the "don't tie it to the in-repo version" rule is respected in substance rather than violated.
• Ran the real bootstrap rather than trusting registry metadata: installed 0.45.0 globally into a temp prefix and ran fjs test — the exact CI command — against this branch: 2976 pass / 0 fail. Worth doing because 0.45.0 carries a **BREAKING CHANGES:** entry (#1520, the npm package ships no .js files); it doesn't affect the bootstrap path.
• nixpkgs 02e08985… exists, compare to nixos-26.05 is identical (pin is exactly at the branch head), https://channels.nixos.org/nixos-26.05/git-revision returns that same SHA, and old→new is ahead_by: 149 so it moves forward. nodejs_22/nodejs_24/nodejs_26 all still resolve at the pinned commit.
• npm run ci-update leaves the tree clean, so the generated ci.yml and three flakes match the config. No stale 9f78f44a anywhere. The two surviving 0.44.0 strings (fjs/ci/packed-consumer-validation.md:76,84) are pre-existing on main and untouched here.
• npx tsc 0, fjs t 2976 pass / 0 fail, cov 100/100/100, prepack clean.

All three addressed — approving.

Title is now ci: bump functionalscript bootstrap version and nixpkgs snapshot, the body carries Changelog: none (right, since no behavior or public API changes, and correspondingly no entry file), and the count reads 11, which is what grep -c '0\.45\.0' .github/workflows/ci.yml gives.

The only new commit is the main catch-up: git diff 7194a2a3 refs/pr/1621 is just fjs/effects/todo/io-effect-consumer-migration.md arriving from #1616, and git diff origin/main refs/pr/1621 is still exactly the five expected files with only the two pin bumps. Nothing of main's is missing.

Still green at b89eb304: npx tsc 0, fjs t 2976 pass / 0 fail, cov 100/100/100, ci-update leaves the tree clean.

Pin verification from the previous pass stands: 0.45.0 is latest on npm and the real fjs test bootstrap passes against this branch, the nixpkgs commit matches what channels.nixos.org/nixos-26.05/git-revision advertises and moves forward 149 commits, and all three nodejs_* attributes resolve at it.