Misspelled user-flags (`-f`) are silently ignored

Misspelled user-flags (`-f`) are silently ignored. In the wild:
```
$ cabal install -w ghc-9.0.1 cabal-plan
...
$ cabal-plan license-report fix-whitespace
ERROR: `cabal-plan license-report` sub-command not available! Please recompile/reinstall `cabal-plan` with the `license-report` Cabal flag activated.
...
$ cabal install -w ghc-9.0.1 -f licence-report cabal-plan
Resolving dependencies...
Up to date
Copying 'cabal-plan' to ...

$ cabal-plan license-report fix-whitespace
ERROR: `cabal-plan license-report` sub-command not available! Please recompile/reinstall `cabal-plan` with the `license-report` Cabal flag activated.
```
Swallowing errors: not a good UI.

Start by reproducing the misspelled `-f licence-report` command shown in the issue, then trace how cabal-install handles user flags during dependency resolution and installation. The work is done when an unknown or misspelled flag is rejected with a clear error instead of being silently ignored, while valid flags continue to work.

Written by the indexing model from the issue text.