Closes shell-injection attack surface in the legacy CJS layer by replacing
all user-controlled run() / runCapture() shell strings with the new argv-safe
runArgv() / runCaptureArgv() helpers. assertSafeName() guards every
user-supplied sandbox/instance/preset name before it enters any command.

bin/lib/onboard.js  -- all openshell/bash/brew calls -> runArgv;
                       file copies -> fs.cpSync/fs.rmSync (no cp shell)
bin/lib/nim.js      -- docker pull/rm/run/stop/inspect -> runArgv/runCaptureArgv;
                       assertSafeName guard on sandboxName
bin/lib/policies.js -- openshell policy get/set -> runCaptureArgv/runArgv;
                       assertSafeName on sandboxName and presetName;
                       temp policy file written with mode 0o600
bin/nemoclaw.js     -- setupSpark: remove inline NVIDIA_API_KEY=VALUE from
                       sudo argv (sudo -E already inherits env);
                       deploy: assertSafeName on instanceName;
                       sandbox connect/status/logs/destroy -> runArgv

Supersedes PRs: NVIDIA#148 (shell injection), part of NVIDIA#330 (credential leak).

… in argv

Fixes: NVIDIA#325 (API key exposed in process list via ps aux)
Supersedes: PRs NVIDIA#191, NVIDIA#330

The root cause: all three execution layers passed the actual credential
VALUE as --credential KEY=VALUE, making it visible to any local user via
`ps aux` or /proc/<pid>/cmdline.

Safe pattern: set the secret in the child's inherited env, then pass only
the env-var NAME to --credential (openshell env-lookup form).

nemoclaw/src/commands/onboard.ts
  - process.env[credentialEnv] = apiKey before execOpenShell
  - --credential arg: credentialEnv (name only, not KEY=VALUE)
  - applies to both provider create and provider update paths

nemoclaw-blueprint/orchestrator/runner.py
  - Rename credential_env -> target_cred_env with type-based fallback
    (nvidia -> NVIDIA_API_KEY, openai -> OPENAI_API_KEY) when not set
    in the blueprint profile. Supersedes PR NVIDIA#191's partial fix.
  - os.environ[target_cred_env] = credential before run_cmd
  - --credential arg: target_cred_env (name only)

nemoclaw-blueprint/blueprint.yaml
  - Add credential_env: NVIDIA_API_KEY to the default profile.
    Without this field the type-based fallback would silently use
    OPENAI_API_KEY for the nvidia provider_type, causing auth failure.

nemoclaw/src/onboard/config.ts
  - writeFileSync for config.json now passes mode: 0o600 so the file
    containing endpoint/model/credentialEnv metadata is not world-readable.

test/credential-exposure.test.js (new file)
  - Static source scan: asserts no --credential KEY=VALUE pattern in any
    of the 3 execution layer files (allowlists dummy/ollama stubs)
  - Layer-specific structural checks (process.env set, os.environ set,
    blueprint default profile has credential_env)
  - Runtime injection PoC: proves old bash -c IS vulnerable; new
    runCaptureArgv IS NOT

All 84 tests pass.