feat(spikes): add Spike 7 desktop git push smoke test

Proves add -> commit -> push over HTTPS+PAT via libgit2 (git2), the
ADR-004 fallback after gitoxide was found to lack HTTP(S) push. Host
crate on stable, kept out of the xtensa firmware tree.

spikes/spike7-git-push/.env.example

@@ -0,0 +1,19 @@
+# Spike 7 (desktop) config. Copy to `.env` and `set -a; . ./.env; set +a` before
+# running against a real GitHub repo. `.env` is gitignored.
+#
+# The working copy to publish. On device this is /sd/repo; on desktop, any
+# clone. Pass as argv[1] or here.
+TW_REPO_PATH=/tmp/spike7-work
+
+# HTTPS + PAT auth (ADR-005). Leave both empty for a local file:// remote —
+# no credentials are needed there. Never logged.
+TW_GH_USER=your-github-username
+TW_PAT=ghp_xxxxxxxxxxxxxxxxxxxx
+
+# Commit author (ADR: author from config). Defaults applied if unset.
+TW_AUTHOR_NAME=Typoena
+TW_AUTHOR_EMAIL=typoena@example.com
+
+# Optional: force origin's URL (e.g. the HTTPS remote baked in at build time).
+# If unset, the working copy's existing `origin` is used as-is.
+# TW_REMOTE_URL=https://github.com/you/typoena-test.git