fix(onboard): preserve Station Express choices on resume

[senthilr-nv]

Summary

DGX Station Express now records its secret-free provider, model, sandbox, and interaction intent before managed vLLM setup can fail. Running nemoclaw onboard --resume restores those choices and retries the failed Express step instead of returning to the generic provider and model prompts.

This draft is stacked on feat/dgx-station-host-prereqs and depends on #6991. Do not merge it first; after #6991 merges, retarget this PR to main and refresh the exact diff.

Related Issue

Fixes #7048

Changes

• Mark only the DGX Station Express installer path so DGX Spark and generic onboarding remain unchanged.
• Persist a versioned, validated, secret-free Station Express resume intent in the existing owner-only onboarding session.
• Restore the managed-vLLM model and Express defaults for failed or interrupted sessions, reject conflicting or malformed state, and clear the intent after successful completion or --fresh.
• Cover initial capture, injected provider failure, failed-session resume, completed provider reuse, cleanup, malformed state, and the Station/Spark installer boundary.
• Correct the command reference to include resumable failed onboarding sessions.

Type of Change

• Code change (feature, bug fix, or refactor)
• Code change with doc updates
• Doc only (prose changes, no code sample modifications)
• Doc only (includes code sample changes)

Quality Gates

• Tests added or updated for changed behavior
• Existing tests cover changed behavior — justification:
• Tests not applicable — justification:
• Docs updated for user-facing behavior changes
• Docs not applicable — justification:
• Sensitive paths changed (security, policy, credentials, preflight, onboarding, inference, runner, sandbox, or messaging)
• Sensitive-path review completed or maintainer-approved waiver recorded — reviewer/approval link/justification: requested on this draft before it is marked ready
• Non-success, skipped, or missing CI check accepted by maintainer — check name, approval link, and follow-up issue:

Verification

• PR description includes a Signed-off-by: line and every commit appears as Verified in GitHub
• Normal pre-commit, commit-msg, and pre-push hooks passed, or npm run check:diff passed when hooks were skipped or unavailable
• Targeted behavior tests pass for the current change set, or tests are marked not applicable above — 140 passed across the six focused onboarding/session files; 87 passed, 1 skipped across the two installer files; npm run typecheck:cli passed
• Applicable broad gate passed — npx vitest run --project cli completed with 9,084 passed, 20 skipped, and four unrelated local failures (missing Python yaml, a temp-directory cleanup race, and two existing five-second timeouts)
• Quality Gates section completed with required justifications or waivers
• No secrets, API keys, or credentials committed
• npm run docs builds without warnings (doc changes only) — passed with zero errors and two existing Fern warnings
• Doc pages follow the style guide (doc changes only)
• New doc pages include SPDX header and frontmatter (new pages only)

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Signed-off-by: Senthil Ravichandran senthilr@nvidia.com

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[github-actions]

PR Review Advisor — Informational

Advisor assessment: Informational / medium confidence
Next action: No advisor follow-up needed.
Findings: 0 blockers · 0 warnings · 0 suggestions
Status: No actionable findings remain in the canonical review ledger.

Model lanes

• GPT-5.6 Terra (primary): Completed · medium confidence · 0 blockers · 0 warnings · 0 suggestions
• Nemotron 3 Ultra (second opinion): Completed · high confidence · 0 blockers · 0 warnings · 0 suggestions
• Model comparison: normalized findings match; normalized E2E selections differ; severity counts match.

Nemotron output stays in workflow artifacts and does not change the assessment above.

E2E guidance

Advisory only. E2E / PR Gate selects and runs jobs independently.

Recommended E2E: cloud-onboard, onboard-repair, onboard-resume

Workflow run details

This automated review informs maintainers. Warnings and suggestions do not require a response. A maintainer decides whether to merge.