fix(install): only create CLI launcher shims when the packaged launcher supports them

[mcoliver]

Fixes #73.

openutv.com/install.ps1 redirects to this file. Since #63's installer changes, it has turned utvio/utvpkg/py-interp/utvls into copies of utv.exe for every release. Only launchers built with #63 dispatch on their own file name, and the current release (2026.9, built 09-27) predates it. So on a fresh Windows install:

1. py-interp.exe (a copy of the 2026.9 launcher) starts the viewer.
2. At startup the help-menu package runs openutv-check-updates.py through bin\\py-interp.exe, which opens another viewer, which checks for updates, which opens another viewer, and so on.

Fix

• Create shims only when the downloaded package ships openutv-run.cmd (post-fix: resolve Windows CLI dependencies and implement OIIO image writing #63 builds). This is checked in the extracted package before it's moved into place, so files from a previous install can't fool it.
• Otherwise, repair installs shimmed by the previous installer: keep the package's real <tool>.exe and remove the stale -bin copy. Re-running the installer fixes affected machines.
• With shim support, always refresh <tool>-bin.exe from the package (previously a stale -bin blocked it).

Verification

Parsed with pwsh, and the shim logic was extracted from this file and run against simulated install folders:

Scenario	Result
2026.9-style ZIP, fresh install	real py-interp.exe / utvio.exe, no -bin
2026.9-style ZIP over a broken shimmed install (the #73 case)	restored real binaries, stale -bin removed
post-#63 ZIP, fresh install	launcher shims + real -bin
post-#63 ZIP over a stale shimmed install	-bin refreshed from the package

Not run on a real Windows machine. The launcher-side hardening (never fall back to the viewer from a tool shim) follows in a separate PR.

The website repo's unused copy (public/install.ps1) is kept in sync in OpenUTV/www.openutv.com@b25b7dd.

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