The v0.1 technical doc still described the gitoxide/gix plan with an
undecided transport and a 32 KB git_task stack. Bring it in line with
what spike 7 proved:
- gix → libgit2 via the git2 crate (ADR-004 kill-switch fired: no gix push)
- transport settled: HTTPS + PAT over esp-idf mbedTLS, no custom transport
or reqwest/rustls layer needed
- fail-closed cert verification (embedded GitHub roots + PASSTHROUGH)
- git_task stack 32 KB → 96 KB (measured ~67 KB depth); dedicated thread
- persistent-clone + fast-forward is the product flow (spike used a fresh
per-boot throwaway branch); add --all stages deletions
- PAT via libgit2 credential callback, never logged/persisted
Also mark the Spike 7 entry done in the spikes list.
2f2f1227ec