loopsmith v0.1.3

The release where Windows stopped being a badge and started being a platform.

Fixed

• which() found nothing at all on Windows. It joined the bare command name
  onto each PATH entry, and executables there are git.exe — so nothing ever
  matched and it returned None for every command on the machine. Every caller
  then faithfully reported the falsehood it was handed: doctor listed every tool
  as absent, Platform::detect found no scheduler, and worktree isolation
  degraded to the shared directory with "git not on PATH" on a runner where
  actions/checkout had just used C:\Program Files\Git\bin\git.exe. The
  schtasks support added in 0.1.0 was dead on arrival for the same reason,
  because which("schtasks") could never succeed. Roughly a third of the Windows
  claim was decoration.

  Each PATHEXT suffix is now tried as well as the bare name, honouring the
  variable rather than hardcoding a list — it is how a machine says .ps1 counts
  as a command. The suffix is appended, not set as the extension, so check.sh
  can become check.sh.exe where set_extension would have produced check.exe.

  Command::new("git") was never affected: Windows' CreateProcess appends the
  extension itself. Only loopsmith's own lookups were broken.

• The generated .cmd launchers reported success when they had failed.
  setlocal saves the current errorlevel and the implicit endlocal at the end
  of a batch file restores it, so a bare exit /b 127 inside a setlocal scope
  exits 0. A loop whose pinned binary had moved printed "loopsmith is not at
  … and not on PATH" and then exited successfully — the precise silent failure
  the exit code exists to prevent, and one a scheduled job would never surface.
  resume.cmd's "no run id given" exit 2 had the same defect, as did the export
  launcher.

  endlocal & exit /b <code> fixes it on a top-level line but not inside a
  nested if ( … ) block, which is where the broken one lived — so each launcher
  now has exactly one exit /b, on its last line, reached by every path via
  goto. They also enable delayed expansion and capture with !ERRORLEVEL!,
  because a parenthesised block is parsed before it runs and %ERRORLEVEL% inside
  one reads the value from before the command. A test asserts the single exit,
  the label, and the absence of parse-time capture.

• loopsmith new closed by telling every user to run run.sh, including on
  Windows where cmd.exe cannot execute it and run.cmd was sitting beside it.
  It now names the launcher the host can run, and prints set rather than
  export for the API-key line there.

Changed

• Every published package now carries a README that stands on its own. The
  crates.io, npm, and PyPI pages previously said little and pointed at the
  repository; someone arriving from a registry had to leave to learn what the tool
  was. Each now explains the design, shows a real config, lists the subcommands,
  and covers install, providers, scheduling, and platform behaviour in the idiom
  of that registry. The eight library crates had no README at all and rendered
  as blank pages; each now explains its own role and where it sits.
• CI no longer downloads a third-party toolchain or cache action. rustup is
  preinstalled on GitHub-hosted runners, and eight consecutive runs lost a leg to
  codeload 429/502/503 while fetching an action — before a line of loopsmith
  compiled. continue-on-error could not save it either: actions are downloaded
  during "Set up job", before the step that was allowed to fail ever runs. A cold
  build takes about two minutes, so the cache was saving less than the flakiness
  cost.
• Two tests that invoked ./run.sh and ./resume.sh directly now pick the
  launcher the host can execute. Gating them with #[cfg(unix)] would have made
  the suite green while leaving the .cmd launchers unexercised on the only
  platform that runs them.