GeezerVison

…kend + build guard

Simplify the cargo apply path to patch crates in place (vendored or
registry cache) like npm/pypi/gem, removing the project-local
`[patch]`-redirect backend and the build-time `socket-patch-guard`
setup wiring. Cargo now rolls back in place from before-blobs rather
than dropping a redirect.

Removed:
- core: `cargo_setup` (discover/update), `patch/cargo_config`,
  `patch/cargo_redirect`, and `go_setup` (the build-time Go guard
  package + templates).
- cli: cargo/go redirect dispatch in `apply`/`rollback`, cargo + Go
  guard wiring in `setup`, and the now-dead setup/redirect tests.

Kept:
- Go `replace`-redirect (`go_redirect`/`go_mod_edit`/`copy_tree`): the
  module cache is checksum-verified, so in-place patching fails
  `go.sum` at build time — Go still needs the project-local copy.
- The `socket-patch-guard` crate and its build-integration test.

`copy_tree` is now gated on `golang` only. Docs (README, CLI_CONTRACT,
module headers) updated to drop the removed backends.

Builds clean across feature combos (default / none / all / cargo-only)
and the full suite passes (--no-fail-fast).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

The simplification deleted `tests/e2e_cargo_coexist.rs` and the
`go_setup/templates/*.tmpl` files, but ci.yml still referenced them:
the e2e matrix listed `e2e_cargo_coexist` (no such target → fail) and
the lint-ecosystems job `cp`'d the now-absent Go guard templates for
gofmt/vet (cp → fail). Remove both; keep `guard_build_integration`.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

…ferences

With cargo patching in place (no `[patch]`-redirect) and `setup` no
longer wiring a build-time guard, the `socket-patch-guard` crate had no
consumer: nothing in cli/core references it, `setup` never writes it,
and its `.socket/cargo-patches/` + `SOCKET_PATCH_ROOT` machinery no
longer exists. Remove it and every dangling reference.

- Delete `crates/socket-patch-guard/` (crate, build.rs, README,
  SAME_TICK_HEAL_RND.md, same_tick_heal_experiment.rs) and drop it from
  the workspace members + Cargo.lock.
- Delete `guard_build_integration.rs`; drop the `guard_build_integration`
  e2e matrix entry and the guard-template gofmt/vet step from ci.yml;
  drop the `cargo publish -p socket-patch-guard` step from release.yml.
- CHANGELOG: rewrite the `[Unreleased]` cargo/guard entries to describe
  what actually ships — cargo in-place patching (default feature) and
  the Go `replace`-redirect backend — and drop the now-false
  "cargo apply now redirects" Changed bullet.
- Drop the dead `SOCKET_PATCH_ROOT`/`SOCKET_PATCH_GUARD` env vars from
  test scrub lists (no longer read in src; `SOCKET_PATCH_BIN` kept — the
  gem Bundler plugin still uses it); repoint stale `setup_matrix_cargo`
  doc-comments to surviving sibling suites; refresh CLI_CONTRACT prose.

Builds clean across feature combos; full suite passes (--no-fail-fast).

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>