Repin the adopter template to a commit that is on a branch

Repin the adopter template to a commit that is on a branch The template pinned e208c21f, which the squash merge of the standard left reachable from nothing: the commit still resolves, and `branches-where-head` returns zero. Actions keeps resolving an unreachable commit for a while, so every repository copying the template would have adopted a commit outside the project's history and found out much later. It now pins e1714a28, the merge commit on main. Two tests guard the pair. One renders the template's own pin and requires the output to equal the committed file, because adopters copy the template while automation runs the renderer, and drift means half the repositories get a file nobody reviewed. That test failed when written: the renderer omitted the thirteen-line copy-in header and half a comment, so regenerating silently dropped the instructions. The other asserts the pinned commit is on a branch. Co-Authored-By: Claude Opus 5 (1M context) Claude-Session: https://claude.ai/code/session_01XmzqahsmAXBn5wJab92jP2