[dajiaohuang]

Summary

Correct three existing README references without changing runtime behavior:

• Include the required switch-action (switch) in the deployment example, and retain the instruction to adapt the example to the user's hosts first. The previous invocation exits during argument parsing even when the deployment file exists.
• Point each build badge to its corresponding active workflow. Both previously linked to build.yaml, which does not exist.
• Use vendorHash, the attribute actually defined in default.nix, in the dependency-update instructions.

Validation

• Built the CLI with Go 1.26.3 on Windows.
• Reproduced the missing switch-action parsing error with an owned tiny fixture. With switch supplied, argument parsing proceeds to a deliberately failing mock build command. No real deployment was performed.
• Exercised help, evaluation, inventory listing, host glob/tag/order/skip/every/limit selection, empty health-check handling, and build-error propagation through the CLI with an isolated synthetic inventory and mock Nix commands (13 cases).
• Confirmed the corrected workflows exist and are active through the GitHub API; the previous build.yaml lookup returns 404.
• git diff --check passes.
• go test -vet=off ./... passes (packages currently have no test files). Plain go test ./... reports an existing non-constant format string at morph.go:740; this PR changes only README.md.
• Nix/flake/example-build/VM checks were not run: this Windows environment has no Nix runtime. No real SSH, secrets, or user configuration was used.