The installers work on npm 12, whose npm ci reads only package-lock.json

[kevin9327]

Fixes #278.

Why

Releases ship their dependency lockfile as npm-shrinkwrap.json (release.yml copies package-lock.json to it before npm pack). npm ci in npm 12 only accepts a package-lock.json, so with npm 12 the one-line install stops with:

npm error code EUSAGE
npm error The `npm ci` command can only install with an existing
npm error package-lock.json with lockfileVersion >= 1. ...

That's the failure in the issue (Fedora 44, Node 24.16, npm 12.0.2). I reproduced it with npm 12.2.0 against the current release tarball (v0.1.206):

	npm 12.2.0	npm 11.19.0
install.sh on main	✖ EUSAGE, "npm couldn't install Agent Office's dependencies"	✔
install.sh with this change	✔ added 28 packages, installed	✔ added 28 packages, installed

(Both runs used AGENT_OFFICE_TARBALL=<downloaded v0.1.206 agent-office.tgz> AGENT_OFFICE_INSTALL_ONLY=1.)

What changed

• install.sh: before npm ci, copy the release's npm-shrinkwrap.json to package-lock.json if the package doesn't already have one. Older npm already prefers the shrinkwrap, and the two files are identical, so they install exactly the same versions as before.
• install.ps1: the same copy in the Windows installer.
• tests/install.test.ts: runs install.sh against a small local release tarball whose only lockfile is npm-shrinkwrap.json. A stand-in npm on PATH behaves like npm 12 (ci fails without package-lock.json). The test checks that npm ci saw both files and that the version is installed and marked current.

This is the same approach as the earlier #284, which its author closed without it being merged. This PR adds the regression test and the npm 12 reproduction above.

Verification

• The new test fails on main with the npm 12 error (npm error The \npm ci` command can only install with an existing package-lock.json→agent-office: npm couldn't install Agent Office's dependencies`) and passes with the change.
• npm run typecheck: passes
• npm test: 607 tests, 607 pass
• npm run build: passes
• bash -n install.sh: passes
• End to end with a real npm 12.2.0 and npm 11.19.0 against the v0.1.206 release tarball (table above), on Linux x86_64.

Not tested: install.ps1 on Windows. I don't have PowerShell or Windows here, so that part has only been reviewed by reading it; it mirrors the bash change line for line.