Add host bootstrap and repair helpers

Add a dedicated pyro host surface for supported chat hosts so Claude Code, Codex, and OpenCode users can connect or repair the canonical MCP setup without hand-writing raw commands or config edits.

Implement the shared host helper layer and wire it through the CLI with connect, print-config, doctor, and repair, all generated from the same canonical pyro mcp serve command shape and project-source flags. Update the docs, public contract, examples, changelog, and roadmap so the helper flow becomes the primary onramp while raw host-specific commands remain as reference material.

Harden the verification path that this milestone exposed: temp git repos in tests now disable commit signing, socket-based port tests skip cleanly when the sandbox forbids those primitives, and make test still uses multiple cores by default but caps xdist workers to a stable value so make check stays fast and deterministic here.

Validation:
- uv lock
- UV_OFFLINE=1 UV_CACHE_DIR=.uv-cache make check
- UV_OFFLINE=1 UV_CACHE_DIR=.uv-cache make dist-check

Makefile

@@ -1,6 +1,7 @@
 PYTHON ?= uv run python
 UV_CACHE_DIR ?= .uv-cache
-PYTEST_FLAGS ?= -n auto
+PYTEST_WORKERS ?= $(shell sh -c 'n=$$(getconf _NPROCESSORS_ONLN 2>/dev/null || nproc 2>/dev/null || echo 2); if [ "$$n" -gt 8 ]; then n=8; fi; if [ "$$n" -lt 2 ]; then echo 1; else echo $$n; fi')
+PYTEST_FLAGS ?= -n $(PYTEST_WORKERS)
 OLLAMA_BASE_URL ?= http://localhost:11434/v1
 OLLAMA_MODEL ?= llama3.2:3b
 OLLAMA_DEMO_FLAGS ?=
@@ -84,6 +85,8 @@ check: lint typecheck test
 dist-check:
 	uv run pyro --version
 	uv run pyro --help >/dev/null
+	uv run pyro host --help >/dev/null
+	uv run pyro host doctor >/dev/null
 	uv run pyro mcp --help >/dev/null
 	uv run pyro run --help >/dev/null
 	uv run pyro env list >/dev/null