adopt-project.py check: refuse a kept file at the shape's pin path, and an unwritable --work-dir, before any leg exists #524

L1-K1: a kept link AT the shape's own pin path passes check and fails execute after both legs. With --pin openGlass@<commit> --pin-source <clone> and contracts/ kept in the root with contracts/shape-pin.yaml -> openglass-pin.yaml: check exits 0 (plan ok); execute exits 1 with FINDING adopt-shape-pin-unreadable after both leg repositories were created and pushed; the first bootstrap exits 1 with shape-pin-manifest-disagree and shape-pin-no-files. place() writes contracts/openglass-pin.yaml first, so the link then leads to a file and the shape's pin goes beside it, under shape/. The same on main and on #504's branch (fin183g, at 1bdffca, a49a0f8 and 053e725); #504 lists it under "Known limits". A real file at contracts/shape-pin.yaml does the same on main, with a pin or without (check 0, execute 1, first bootstrap 1 yaml-unparsable): check finds no kept path AT the shape's pin path. Direction: find one before any leg exists, as _kept_pin_findings (adopt-project.py:420) does for a declared pin's file. Measured on main 8beb3d9.
— #457, comment

L1-K10 (#183): an unwritable --work-dir is met only after both leg repositories exist. With a work directory the user cannot write (chmod 500), check --work-dir <dir> exits 0 (plan ok) and execute --work-dir <dir> exits 2 with REFUSED extracting the spec leg. after both leg repositories were created and pushed, whether a link sits ABOVE a path the shape writes (.github -> ci) or not. #504's branch does the same since f8e7176 (rv183f). Direction: have execute make and remove a directory in its work directory before it creates a leg repository, and refuse naming that directory. Measured on main 8beb3d9.
— #457, comment