SolarLens v2.5.0

Renewing and updating a relay now shows nothing when nothing needs doing.

Changed

• The login check runs hidden, and a window opens only when a login is
  needed. Since 2.4.0, renew-solis-login.cmd and every re-run of the
  installer opened a visible Chrome window to check the saved SolisCloud login,
  even when it worked, which is most weeks. On a machine that needed nothing,
  a browser appearing and a terminal waiting looked like something going
  wrong. Both now check in a hidden browser first. When the login works, a
  reading goes through and nothing appears. When SolisCloud wants a login, a
  window opens for it and closes itself once a reading has been sent. The check
  also skips the alarm history and period totals, so it takes about twenty
  seconds instead of a minute; the background relay started straight afterwards
  reads them.
• The .cmd windows close themselves when the run worked.
  renew-solis-login.cmd and setup-relay.cmd used to end on "press any key",
  and a personalised setup-solarlens-relay.cmd waited twenty seconds. All three
  now close five seconds after success, and stay open only after a failure, so
  its reason can still be read.
• The installer skips what is already in place. Dependencies are installed
  only when package-lock.json changed since the last install, and a relay task
  someone disabled is left disabled rather than switched back on. Its .dev.vars
  now says RELAY_HEADLESS=1 from the start.

Added

• The installer installs Google Chrome when it is missing, with winget, as
  it already did for Node and Git. It used to warn and carry on, leaving a relay
  that could not start a browser.
• RELAY_SKIP_EXTRAS=1, and distinct exit codes for a single run
  (RELAY_ONCE=1): 0 a reading went through, 3 SolisCloud wants a login,
  1 anything else.

Fixed

• A relay with no working login could report success. It checked for the
  login page once, three seconds after opening the portal. Measured with no
  login at all, the portal stays on the plant page for about three seconds and
  moves to its login page between three and five, so the check could miss it.
  The cycle then sent no reading, logged the timeout as a per-plant error, and
  reported success, and a single run told the installer a reading was through.
  The relay now watches until the plant list loads or the login page appears,
  and a cycle that sends no reading counts as failed. A login lost part-way
  through a cycle is reported as a login to renew.
• The background relay can no longer show a browser window.
  scripts\relay-hidden.vbs forces RELAY_HEADLESS=1 for the relay it starts.
  Before, it followed .dev.vars, where a 0 left by a login done by hand, or
  by an installer run that stopped part-way, put a Chrome window on screen at
  every logon.
• A relay can no longer leave its browser open when it exits. If Chrome
  does not close within fifteen seconds, the relay closes it the hard way.
• A relay attached to your own Chrome (RELAY_CDP) is no longer refused as
  having no saved session when run hidden.
• renew-solis-login.cmd and setup-relay.cmd no longer trip over their own
  update. Both run a script that pulls new code, and that can replace the
  .cmd file itself while it is still running. cmd reads a batch file a line at
  a time and carries on from the same byte offset in whatever the file now
  says: in a test, a file rewritten under a running batch went on to run half a
  line as a command. Each is now one parenthesised block, which cmd reads whole
  before running any of it. This protects updates from 2.5.0 on; the files in a
  2.4 checkout are still the old shape, so move a computer to 2.5.0 with
  setup-solarlens-relay.cmd, which lives outside the repository.

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Deploying: nothing to deploy; the Worker and the dashboard are unchanged. Move each relay computer to 2.5.0 by double-clicking setup-solarlens-relay.cmd, not renew-solis-login.cmd: the 2.4 copy of renew-solis-login.cmd is replaced by this update while it runs. After this update, either is safe. Regenerate setup-solarlens-relay.cmd with scripts\make-laptop-installer.ps1 for its five-second close. The full entry is in CHANGELOG.md.