feat(rust-sdk): auto-install rustup targets on target=; update hm init template + docstrings

CLAUDE.md

@@ -18,3 +18,29 @@ Both DSLs live inside `crates/hm-dsl-engine/` so they ship with the crate:
 
 - `crates/hm-dsl-engine/harmont-py/` — the `harmont` Python package (pipeline DSL).
 - `crates/hm-dsl-engine/harmont-ts/` — the `harmont` TypeScript package (pipeline DSL).
+
+## Keep the SDK, `hm init` templates, and docs in sync
+
+The toolchain helpers in `crates/hm-dsl-engine/` (e.g.
+`harmont-py/harmont/_rust.py`, `harmont-ts/src/toolchains/rust.ts`) are the
+**public authoring SDK**. They have two downstream surfaces that drift silently
+unless you update them in the same change. **A toolchain change is not done until
+all three agree:**
+
+1. **`hm init` templates** — `crates/hm/src/commands/init_templates/<lang>.py`,
+   embedded into the binary via `include_str!` in `crates/hm/src/commands/init.rs`.
+   When you change a toolchain's recommended entrypoint (e.g. Rust →
+   `rust.project().ci()`), update the matching template so scaffolded projects use
+   the current API. Roundtrip tests: `crates/hm/tests/cmd_init.rs`.
+
+2. **Pipeline-SDK reference docs** —
+   `docs-site/content/docs/pipeline-sdk/reference/toolchains/<lang>.mdx` are
+   **auto-generated from the Python docstrings** in `harmont-py` (griffe →
+   `docs-site/scripts/extract-dsl-api.py` → `generate-dsl-docs.ts`); they carry a
+   "do not edit" header. So: (a) write/refresh the docstring on any method you add
+   or change, then (b) regenerate from the simci repo root with `make docs-generate`
+   (DSL-only: rebuild `docs-site/dsl-api.json` from `harmont-py`, then
+   `cd docs-site && npx tsx scripts/generate-dsl-docs.ts && npx tsx scripts/check-dsl-pages.ts`),
+   and (c) commit the regenerated `*.mdx` in the **simci (parent) repo** alongside
+   the gitlink bump. `check-dsl-pages.ts` guards that the committed pages match the
+   docstrings.